A hidden history in the Burgos Cathedral (Spain): virtual reconstruction of light effects generated in the 15th-century chapel of the Conception of Our Lady or St. Anne

Ezequiel Uson Guardiola, José Antonio Gárate Alcalde, Víctor Jørgensen-Mínguez, Eva Espuny Camacho

doi:10.37190/arc250203

Abstract

Special light effects, popularly known as “light miracles,” appear during solstices or equinoxes in three medieval churches located in the Spanish city of Burgos and its surroundings. These hierophanies can be observed in sacred buildings whose design and construction were carried out by medieval architects associated with the so-called “taller de los Colonia” workshop. The underlying assumption of this research is that the same effects were also generated in the Chapel of the Conception of Our Lady in Burgos Cathedral and were visible until the construction of the chapel of St. Thecla in the 18th century. This article virtually reconstructs these light effects using solar lighting simulation software and analyzes the methods of their generation.

Full article view is only available on bigger screens.

2025

2(82)

Ezequiel Uson Guardiola*, José Antonio Gárate Alcalde**,

Víctor Jørgensen-Mínguez***, Eva Espuny Camacho****

A hidden history in the Burgos Cathedral (Spain):

virtual reconstruction of the lighting effects

generated in the 15

century

Chapel of the Conception or Saint Anne

DOI: 10.37190/arc250203

Published in open access. CC BY NC ND license

Abstract

Special lighting eects, popularly known as “the miracles of light”, take place at the solstices or equinoxes in three medieval churches located

in the Spanish city of Burgos and its surroundings. These hierophanies can be observed in religious buildings whose design and construction were

carried out by medieval architects associated with what is known as “taller de los Colonia”. The underlying assumption of the research is that the

same eects were also generated in the Conception Chapel of Burgos Cathedral and were visible until the Chapel of Santa Tecla was built in the 18

century. This paper virtually reproduces these lighting eects using solar simulation software tools and analyses the methods used to generate them.

Key words: lighting eects, workshop of Juan de Colonia, Burgos cathedral, conception chapel, solar simulation software

Introduction

In the late Gothic phase of the construction of the Burgos

Cathedral, the gure of Juan de Colonia (c. 1410–c. 1479)

stands out above all. This magister operis architect of

Ger man origin revolutionized the architectural panorama

of Burgos in the mid-15

century. According to the tra-

ditional historiographical account, he arrived in Burgos

at the beginning of 1440 with the help of Bishop Alon-

so de Cartagena, who brought him back from the Coun cil

of Basel with the task of nishing the cathedral towers

with two openwork spires following Central European

models.

In the main church in Burgos he built the spires of the

towers (1442–1458) and a spectacular dome in dialogue

with them (c. 1470). This last construction collapsed in

1539, being replaced by the Renaissance dome that we see

today. He is also credited with the chapel of the Visitation

(c. 1440–1442) in the same cathedral, the parapet of the

triforium (from 1450) and the design and beginning of the

chapel of the Conception (c. 1477). He also designed and

began the works on the Cartuja de Miraores and was pos-

sibly involved in the renovation of the churches of the mon-

asteries of San Juan and San Pedro de Cardeña and in the

construction of the church of San Nicolás de Bari in Burgos.

Juan de Colonia made a decisive contribution to renew-

ing a local architecture anchored in the Gothic tradition of

the 13

and 14

centuries. His main contributions were

improvements in construction technology, innovations in

vault systems and the introduction of a new spatial model

based on spaciousness, openness and the elevation of the

height of buildings (Menéndez-González 2022).

* ORCID: 0000-0002-0257-314X. UPC Universitat Politècni-

ca de Catalunya – Barcelona Tech, Spain, e-mail: ezequiel.uson@upc.edu

** ORCID:

0009-0008-1321-8099. Metropolitan Chapter of Bur -

gos,

Spain.

*** ORCID:

0009-0006-3622-0779. School of Professional and

Exe cutive Development, UPC Universitat Politècnica de Catalunya – Bar-

celona Tech, Spain.

**** ORCID:

0009-0003-4364-6848. School of Professional and

Exe cutive Development, UPC Universitat Politècnica de Catalunya– Bar-

celona Tech, Spain.

26 Ezequiel Uson Guardiola, José Antonio Gárate Alcalde, Víctor Jørgensen-Mínguez, Eva Espuny Camacho

Two of the six children of the German architect, Simón

and Diego, were also magister operis architects, and the

former achieved a relevance comparable to that of his fa-

ther. Simón de Colonia (c. 1450–1511) is a key gure in

late Gothic architecture in Burgos. His production is char-

acterized by the introduction of innovative ribbed-open-

work vaults and by the great prominence of sculptural

decoration. He trained in his father’s workshop, succeed-

ing his father as master builder of the cathedral from 1481

onwards and taking charge of completing the projects that

the latter had begun before his death, such as the chapel of

the Conception in the Cathedral of Burgos or the church

of the Cartuja de Miraores (Justi 1913).

Between 1482 and 1494 he built what is considered his

great masterpiece, the Chapel of the Purication or the

Constable. In it he executed a spectacular openwork vault

that would be widely imitated in Burgos architecture well

into the 16

century.

In the city of Burgos he also built the Casa del Cordón

(the urban palace of the Constables of Castile), and worked

on the churches of San Nicolás and San Gil. Outside Bur-

gos, the cloister of the monastery of San Salvador de Oña

and the façades of the churches of Santa María de Aranda

de Duero and the convent of San Pablo in Valladolid stand

out (Payo-Hernanz, Matesanz del Barrio 2015).

The architects of the so-called Colonia workshop are

particularly known for their ability to incorporate surpris-

ing lighting eects into their works (Sánchez-Ameijeiras

2001). The phenomenology of light was of great impor-

tance in the medieval Christian imagination. In this sense,

the Colonia workshop has bequeathed to posterity the hie-

rophanies visible in the churches of San Juan de Ortega,

Santa María de Miraores and San Nicolás de Bari, all

of them located in the city of Burgos and/or its surround-

ings. These lighting eects, popularly known as “miracles

of light”, always occur on specic dates in the liturgical-

astronomical calendar.

The chapel of the Conception of the Virgin

of the cathedral of Burgos

The premise of this research is that, in addition to the

three churches mentioned, these same lighting eects were

produced in the Chapel of the Conception of the Virgin

(Fig. 1) of the cathedral of Burgos until the chapel of Santa

Tecla was built in the 1

half of the 18

century, attached

to its southwest side, and, as a consequence, the source of

natural light that caused them was blinded, an oculus locat-

ed in the highest part of the southwest wall, just in front of

the main altarpiece of the chapel (Figs. 2a, b, 3)

As we have demonstrated using solar simulation soft-

ware, before the oculus was blinded in the 18

century,

a beam of sunlight penetrated through it during the spring

and autumn equinoxes and travelled diagonally across the

main altarpiece, from left to right and from bottom to top,

briey illuminating its main theme, the embrace of Saint

Joachim and Saint Anne, the parents of the Virgin Mary,

before the Golden Gate of Jerusalem.

The Chapel of the Conception of the Virgin, located in

the Gospel nave of the cathedral, next to the north arm of

the transept, began to be built in 1477 by order of Luis

de Acuña y Osorio, Bishop of Burgos between 1456 and

1495, with the intention of converting it into his funeral

chapel, just as his predecessor, Alonso de Cartagena, had

done a few years earlier in the south arm of the transept

with the Chapel of the Visitation (Martínez-Sanz 1866).

Although there is no documentary evidence to conrm

this, the construction of the chapel of the Conception has

traditionally been linked to Juan de Colonia, who is said to

have been in charge of the works until his death. Later, his

son Simón, after redesigning the initial project was respon-

sible for completing it (Menéndez-González 2009).

The chapel has an irregular rectangular oor plan cov-

ered by two sections of complex tierceron vaults. The con-

struction had to adapt to the peculiarities of a space that was

highly conditioned by the presence of the buttresses of the

side nave and the northern arm of the cathedral transept, as

well as by the layout of the current Fernán González Street.

The chapel opens onto the gospel nave through two large

pointed arches, which in turn are closed with two railings

from the period. The space was illuminated through three

openings to the outside, two pointed windows to the north-

west and southeast and the aforementioned oculus to the

southwest.

But this chapel is best known for its extraordinary altar-

piece, the work of Gil de Siloe (sculpture) and Diego de

la Cruz (polychromies), who executed it between 1483

and 1486 (Fig. 4). It is a very novel altarpiece for Cas-

tile at the time, both for its structure and its iconography.

It features the monumental Tree of Jesse, or genealogical

tree of Christ, located in the central street, whose branches

ascend the altarpiece surrounding the large rectangle that

frames the main theme, the Embrace before the Golden

To build the chapel of Santa Tecla, four small medieval chapels

that faced the gospel nave of the cathedral and the parish church of

Santiago de la Fuente, which was located behind them, were demol-

ished.

Fig.1. The Cathedral of Burgos, Spain.

View of the entrance to the Chapel of the Conception of the Virgin

(photo by J.A. Gárate-Alcalde)

Il. 1. Katedra w Burgos, Hiszpania.

Wnętrze – widok na wejście do kaplicy Poczęcia NMP

(fot. J.A. Gárate-Alcalde)

A hidden history in the Burgos Cathedral (Spain) 27

Fig. 2. The cathedral of Burgos, Spain:

a) image of the blinded oculus of the Chapel of the Concepcion as it appears today,

b) section showing the Chapel of the Conception (15

century) between the Chapel of Santa Tecla (18

century)

and the northern arm of the cathedral transept (13

century) with the position of the blinded oculus framed in red

(elaborated by V. Jørgensen)

Il. 2. Katedra w Burgos, Hiszpania:

a) zaślepiony okulus kaplicy Poczęcia NMP, stan obecny,

b) przekrój ukazujący kaplicę Poczęcia NMP (XV w.) pomiędzy kaplicą pw. św. Tekli (XVIII w.)

a północnym ramieniem transeptu katedry (XIII w.) z pozycją zaślepionego okulusu obramowanego na czerwono

(oprac. V. Jørgensen)

section A-A

Fig. 3. The cathedral of Burgos, Spain.

Plan – the Chapel of the Concepcion framed in red

(elaborated by V. Jørgensen)

Il. 3. Katedra w Burgos, Hiszpania.

Rzut – kaplica Poczęcia NMP zaznaczona na czerwono

(oprac. V. Jørgensen)

28 Ezequiel Uson Guardiola, José Antonio Gárate Alcalde, Víctor Jørgensen-Mínguez, Eva Espuny Camacho

Gate of Jerusalem. This unusual theme, which comes from

the apocryphal gospels, is a reference to the immaculate

condition of the Virgin Mary, a mystery that was debated

in those nal years of the 15

century and to which Bishop

Luis de Acuña dedicated the Chapel (Yarza-Luaces 2000,

pp. 42, 43 and 80, 81).

Generation of lighting effects

in medieval Christian temples

The lighting eects that occur on certain days of the

litur gical-astronomical calendar in religious buildings in

the Burgos area are not an isolated event.

Numerous cases of surprising lighting eects have been

documented in medieval European ecclesiastical architec-

ture,

which can be concluded to be no coincidence. Well-

known similar examples include those that occur at the

summer solstice in the Abbey of Chiaravalle della Colom-

ba (1135), Abbey of Pomposa (1026), Basilica of Santa

Maria Magdalena in Vezelay (1140), in the Baptistery of

Parma (1196) (Incerti 2013, 2015) and at the equinoxes in

the pulpit of Strasbourg Cathedral (1493) (Becker 2021).

These lighting eects always occur on special dates in

the astronomical calendar of pagan origin. This can be ex-

plained by the fact that the Christian calendar contains a cy-

cle of four festivals that became the solstice and equinox

Fig. 4. The cathedral of Burgos, Spain. Image of the northeast side of the Chapel of the Conception in which the altarpiece by Gil de Siloe

can be seen with the sculptural group of the embrace of St. Joachim and St. Anne located in its centre

(elaborated by V. Jørgensen)

Il. 4. Katedra w Burgos, Hiszpania. Północno-wschodnia ściana kaplicy Poczęcia NMP z ołtarzem autorstwa Gila de Siloe

z rzeźbiarską grupą obejmujących się św. Joachima i św. Anny przy bramie Jerozolimy umieszczoną w jego centrum

(oprac. V. Jørgensen)

A hidden history in the Burgos Cathedral (Spain) 29

dates with theological and cosmological symbolism. These

four days, located next to the astronomical solstices and

equinoxes, celebrate the Annunciation on March 25

, the

birth of Christ on December 25

(Christmas), and the con-

ception and birth of Saint John on December 24

and June

. In his sermons, Saint Augustine makes clear the con-

trast between the pagan cult of the visible Sun and the cult

of Jesus Christ, the Christian creator of the sun, the sun of

justice (McCluskey 1993).

The identication of light with the sacred in medieval

art and architecture reinforces the thesis that these phe-

nomena are not the result of chance, but were intentionally

generated in order to emphasize the story represented in

certain sculptural groups inside these buildings.

Now, in order to attribute an astronomical intention to

these light phenomena that occur in some medieval churches,

it is important to carefully assess the knowledge that these

architects possessed:

To generate these eects, three types of problems must

be solved in the design and construction of the building.

– An astronomical problem: the alignment of the build-

ing with visible points on the horizon that coincide with

the rising or setting of a celestial body (sun, planets, stars

or moon) on signicant dates of the year.

– A geometric problem: the position of the openings

and their relationship to the oor plan and elevation of the

building so that the entry of sunlight at specic times illu-

minates certain sculptural groups inside.

– An ornamental problem: the design and position of

the sculptural elements so that a certain image would be

reached by the ray of light on a specic day of the astro-

nomical calendar (Incerti 2015).

Geometry and astronomy in the training

of medieval architects

Although we do not know exactly all the geometric

canons that were used to generate these lighting eects,

it is clear that some medieval architects had the necessary

knowledge of astronomy and geometry to do so. Their

training, acquired rst in monastic and cathedral environ-

Fig. 5. Determining the position of openings using the gnomon: a) determination of the height of the opening using Thales’ theorem

(source: Vilas-Estevez, Varela and Gonzalez-Garcia 2018), b) diagram (elaborated by E. Uson)

Il. 5. Określenie pozycji kąta padania promieni za pomocą gnomonu: a) określenie wysokości z użyciem twierdzenia Talesa i wykorzystaniem

otworów gnomonu (źródło: Vilas-Estevez, Varela i Gonzalez-Garcia 2018), b) diagram (oprac. E. Uson)

ments and later in universities, was based on two blocks

of disciplines, the trivium (grammar, rhetoric and dialec-

tics) and the quadrivium (arithmetic, music, geometry and

astronomy), which, in turn, came from the “seven liberal

arts” taught in the classical world and were transmitted to

the medieval world through successive translations and re-

productions of ancient texts.

The knowledge of geometry of the architects of the

“Colonia workshop” is evident in their buildings, especial-

ly in their vaulting systems. The vaults they built in some

chapels of the Burgos Cathedral are based on complex

geometric gures that are impossible to design without

a minimum knowledge of Euclidean geometry. This can be

seen above all in the star-shaped and openwork vault of the

chapel of the Purication or of the Constable (De la fuen-

te-Martínez, García-Velasco and Gordillo-Alonso 2021).

Geometrical tools and procedures supposedly

used by medieval architects

to produce lighting effects

In order to determine the trajectory of the ray of sunlight

with simple geometric operations and to transfer the results

to the full-scale layout on the ground, medieval architects

had tools such as the gnomon, the astrolabe, the Vitruvi-

an analemma and the Ptolemaic analemma. These tools

allowed them to determine the azimuth of sunrise on any

day of the year and the celestial coordinates throughout the

hours. With these instruments, knowledge of Euclidean ge-

ometry and the help of scale models or, much more simply,

very basic and simplied graphics, using Thales’ theorem

and laying out two similar right triangles, they could mea-

sure any height simply by using a gnomon

(Fig. 5a, b).

The height of the opening in the exterior wall of the building is

obtained by applying the formula h=dxh1/d1, whit d1 being the distance

between the gnomon and the shadow cast, h1 the height of the perfora-

tion of the gnomon and d the distance between the shadow cast and the

wall in which the opening is to be made. This method may have origi-

nated with Fibonacci, whose treatise De Practica Geometria (1220) was

studied in medieval schools (Hughes 2008).

30 Ezequiel Uson Guardiola, José Antonio Gárate Alcalde, Víctor Jørgensen-Mínguez, Eva Espuny Camacho

Thus, a good architect could choose the exact position of

those openings that, placed at topologically signicant

points, would guarantee surprising lighting eects.

A recent study on the lighting eects produced in the

cathedral of Santiago de Compostela demonstrates the va-

lidity of the method that could have been used by medi-

eval architects to create them (Vilas-Estévez, Varela and

González-García 2018). Using the gnomon, they possibly

solved it empirically with some ease. However, although

the issue of determining the position of openings and orna-

mental elements to be illuminated can be resolved theoret-

ically with relatively simple graphic calculations, achiev-

ing the illumination of a certain sculptural group inside the

temples on a certain day of the year and at a certain time of

day is a much more complex issue.

With a gnomon, the position of the sun and its trajecto-

ry can be determined, and once the position of the image of

the interior of the temple to be illuminated has been estab-

lished, the position of the opening through which the ray

of sunlight will penetrate on the dates on which the light-

ing eect is to be produced can also be established. To do

this, it will be necessary to calculate, in addition to the alti-

tude and azimuth, the basic data of the opening: its position

from the ground and its dimensions. A second possibility

would be to establish the position and size of the opening

and move the decorative element until the correct position

is found. And all this, as is usual in architectural construc-

tion, can be veried empirically during the layout phase of

the building in its nal location.

In relation to this methodology, it is important to draw

attention to a peculiarity of the Chapel of the Conception

in Burgos Cathedral. If we look at the oculus on the south-

west wall, it is centred with respect to the arch of the main

Fig. 7. Location of the Chapel of the Conception

from Google Earth

(elaborated by E. Espuny Camacho, source: Google)

Il. 7. Lokalizacja kaplicy Poczęcia NMP – widok z Google Earth

(oprac. E. Espuny Camacho, źródło: Google)

vault. However, the large niche that houses the altarpiece

of the chapel appears clearly o-centre with respect to the

arch of the vault. This asymmetry could be related to the

elabo ration of the lighting eect that was produced in

the chapel.

Virtual reconstruction

of the lighting effect

of the Chapel of the Conception of the Virgin

of Burgos Cathedral

To virtually recreate the lighting eects that occurred

in the chapel of the Conception of the Virgin of the Ca-

thedral of Burgos, an original methodology has been used,

already used in other previous investigations (Uson-Guar-

diola 2023), which is based on the use of solar simulation

software tools and whose phases are described below.

1. Survey of the chapel with 3D digital scanning and

subsequent restoration carried out from the point cloud

with the SketchUp 2023 Extension Trimble Scan Essen-

tials program (Fig. 6) (SketchUp. 2024).

2. Positioning of the chapel with marking of the azi-

muth of the main axis of Burgos Cathedral and determi-

nation of its geographical coordinates (Fig. 7). Obtaining

from Google Earth the geographical coordinates of Bur-

gos Cathedral (42°20′26″N 3°42′16″W) and the orienta-

tion of the main axis of the Chapel of the Concepcion

(221° measured from the north in a clockwise direction)

(Fig. 7).

3. Creation of the EPW (Energy Plus Weather File)

with the Meteonorm 8 software once the exact position of

the chapel is known and the topographic horizon is deter-

mined. In this case, it is obtained that at the equinoxes. The

polar coordinates at the time of sunrise would be an azi-

muth of 92° and a solar altitude of 2° (Meteonorm 8. 2024).

4. Preparation of the stereographic solar diagram made

with Andrew Marsh’s application (a rst approximation)

(Fig. 8).

5. To determine the days and times when the images on

the altarpiece would have been illuminated by the sun’s

rays penetrating the interior space through the currently

closed oculus, we used Andrew Marsh’s Sun-Path appli-

cation on the three-dimensional survey of the chapel (An-

drew Marsh Software 2025).

Fig. 6. Three-dimensional survey of the Chapel of the Conception

from digital scanning

(elaborated by E. Espuny Camacho)

Il. 6. Trójwymiarowy obraz kaplicy Poczęcia NMP utworzony

na podstawie skanowania cyfrowego (oprac. E. Espuny Camacho)

A hidden history in the Burgos Cathedral (Spain) 31

Fig. 9. Mapping of the annual direct solar reception

of the sculptural group of the Embrace of St. Joachim and St. Anne

(elaborated by E. Espuny Camacho)

Il. 9. Mapowanie rocznego bezpośredniego nasłonecznienia

grupy rzeźbiarskiej obejmujących św. Joachima i św. Anny

(oprac. E. Espuny Camacho)

Fig. 8. Stereographic diagram made with Andrew Marsh’s application

at the spring equinox

(elaborated by E. Espuny Camacho, source: Andrew Marsh Software)

Il. 8. Schemat stereograficzny prezentujący obiekt w czasie

równonocy wiosennej wykonany przy użyciu aplikacji Andrew Marsha

(oprac. E. Espuny Camacho, źródło: Andrew Marsh Software)

This allows us to determine the azimuth and height of

the sun for the period studied. This gives us a rst approx-

imation of the day and time when the altarpiece receives

sunlight. In this case, it turns out that the sculptural group of

the embrace of St. Joachim and St. Anne was illuminated by

solar radiation and with varying intensities for a few days

around the spring equinox (the Christian feast of the An-

nunciation) and the autumn equinox, and that the light beam

was projected with maximum intensity and more focused

on the sculptural group. This it occurred specically at the

spring equinox on March 20 at 14:34 solar time (when the

sun has an azimuth of 223.50° and a height of 38.19°).

6. To simulate the dierent times of the year when

the sun passed through the oculus and to check the result

obtained with the Sun-Path application, the 3D model,

made from the point cloud obtained by digitally scanning

the Chapel and the climate le,were imported into the

Archiwizard 2020 software (Graitec Archiwizard Software

2025). By placing a solar receiver on the sculptural group

of the embrace of Saints Joachim and Anne, when simu-

lating annual direct solar radiation, the result is also that

it would receive solar radiation for a few days in the 2

half of March and a few days in the 2

half of September

coinciding with the equinoxes (Fig. 9).

The spring equinox currently takes place in the north-

ern hemisphere between March 20 and 21 and the autumn

equinox between September 22 and 23.

Simulation of the light eect generated by the sun over

the course of an hour (Fig. 10a) and determination of the

moment when the solar radiation would be cantered on

the main image of the altarpiece (Fig. 10b).

The sculpture of the embrace of Saint Joachim and

Saint Anne would receive maximum radiation on March

20 between 15:00 and 16:00 UTC (winter time in the EU),

which corresponds to 14:00 and 15:00 solar time. Like-

wise, on September 24 it would receive maximum radia-

tion between 16:00 and 17:00 UTC (summer time in the

EU), which corresponds to 14:00 and 15:00 solar time.

8. Simulation of the light eect generated by the sun on

the three-dimensional image obtained from the 3D digital

scan (Fig. 11a, b).

Conclusions

We believe that the lighting eects produced in medi-

eval religious buildings designed by the architects of the

Colonia workshop in the city of Burgos and its surround-

ings are not the result of chance, but the result of a pre-

conceived plan, and good proof of this is the case of the

chapel of the Conception of the Virgin of the Cathedral of

Burgos, the subject of this research. It has been possible to

verify through the use of a solar simulation methodology

with software tools that Simón de Colonia intentionally

established where the light source should be and where and

how the main sculptural element of the altarpiece should

be located and designed to receive spectacular lighting on

certain dates of the astronomical calendar. This fact, that

is, the supposed intentionality of the lighting phenomenon,

would imply the dependence of the conguration of the al-

tarpiece on the desired eect and, logically, a great rapport

between architect and sculptor

. It is therefore worth ask-

ing whether the search for this type of eect could be be-

Let us remember that Simón de Colonia and Gil de Siloe were

regular collaborators. In a short space of time they worked together in the

chapel of the Conception, in the Cartuja de Miraores and in the chapel

of the Purication or of the Constable. In addition, both, together with the

painter Diego de la Cruz, polychromies of the main altarpieces of these

constructions, belonged to the same brotherhood, that of Santiago and

San Andrés of the parish of Santiago de la Fuente. On the latter (Ibáñez

Pérez, Payo Hernanz 2008).

32 Ezequiel Uson Guardiola, José Antonio Gárate Alcalde, Víctor Jørgensen-Mínguez, Eva Espuny Camacho

Fig. 11. Simulation of the lighting effect on the 3D restoration of the Chapel of the Conception obtained from the digital scan:

a) side view with oculus,

b) altar view with the highlighted group of St. Joachim and St. Anne embracing – the moment of Conception of St. Mary

(elaborated by E. Espuny Camacho, source: Graitec Archiwizar Software)

Il. 11. Symulacja oświetlenia w modelu 3D kaplicy Poczęcia NMP opracowana na podstawie skanowania cyfrowego:

a) widok boczny z okulusem,

b) widok ołtarza z oświetloną grupą obejmujących się św. Joachima i św. Anny – momentu Poczęcia Maryi

(oprac. E. Espuny Camacho, źródło: Graitec Archiwizar Software)

Fig. 10. Simulation of the path of solar radiation on the sculptural group

of the Embrace of St. Joachim and St. Anne:

a) (from left to right and from bottom to top) between 14:00 and 15:00. on March 20 and September 24,

b) simulation of the exact moment, 14:34 on March 20,

when the image of the embrace would be fully illuminated

(elaborated by E. Espuny Camacho, source: image obtained with the simulation carried out with the Graitec Archiwizard Software)

Il. 10. Symulacja ścieżki światła słonecznego na rzeźbiarskiej grupie

obejmujących się św. Joachima i św. Anny:

a) (od lewej do prawej i od dołu do góry) między godziną 14:00 a 15:00 w dniach 20 marca i 24 września,

b) symulacja dokładnego momentu, 14:34 w dniu 20 marca,

kiedy widok objęcia się rodziców Maryi byłby w pełni oświetlony

(oprac. E. Espuny Camacho, źródło: obraz uzyskany za pomocą symulacji przeprowadzonej przy użyciu oprogramowania Graitec Archiwizard)

A hidden history in the Burgos Cathedral (Spain) 33

Acknowledgements

We would like to thank the Metropolitan Chapter of Burgos for the facili-

ties provided to access the cathedral and to be able to obtain and compare

all this information.

References

Andrew Marsh Software. “Software Development.” Accessed April 15,

2025. http://www.andrewmarsh.com/software.

Becker, Caroline. “El misterioso rayo verde de la Catedral de Estras-

bur go.” Published September 28, 2021. Accessed April 10, 2025, at

https://es.aleteia.org/2021/09/28/el-misterioso-rayo-verde-de-la-cat-

edral-de-estrasburgo/.

De la Fuente-Martínez, Constantino, Juan Jesús García-Velasco, and

Alfredo Gordillo-Alonso. “Capítulo III. Capilla de los Condestab-

les.” In Tesoros matemáticos de la catedral de Burgos, edited by

Sociedad Castellana y Leonesa de Educación Matemática “Miguel

de Guzmán,” 2021.

hind the original compositions of some of the altarpieces

on which Gil de Siloe and Simón de Colonia collaborated

(the chapel of the Concepción and the church of the Cartu-

ja de Miraores).

To understand why the architects of the Colonia work-

shop created lighting eects in their religious buildings, we

must take into account the importance that the “theology

of light” had in the medieval Christian imagination. In me-

dieval architecture and art, light takes on a transcendent

meaning; it is used as a symbolic reference to the sacred,

as a manifestation or expression of God (Nieto-Alcaide

1989). This idea, this identication of light with the sacred,

is based on the numerous references existing in the gos-

pels and will be strongly felt throughout the Middle Ages.

Thus, the antagonism between light and darkness will be an

ideal vehicle for the expression of religious mysteries and

from the earliest times it was used to inspire devotion by

contrasting the “heavenly light” with the darkness of hell.

Regarding the symbolic meaning of the lighting eect

analysed, this is closely related to the meaning of the scene

represented in the central element of the altarpiece. When

it came to nding an image that would eectively convey

the idea of the immaculate conception of Mary, the ele-

gant theme of the embrace of her parents, Saint Joachim

and Saint Anne, in front of the Golden Gate of Jerusalem,

would end up prevailing in the medieval Hispanic world

(Vilas-Estévez, Varela and González-García 2018).

It should be noted that the representation of divine in-

tervention in miraculous conceptions by means of a beam

of sunlight penetrating an interior space through an open-

ing (normally an oculus) is quite common in artistic rep-

resentations of the period in question. This appears, for

example, in two Annunciations on the backs of the choir

stalls of Burgos Cathedral itself (Fig. 12)

As for the impact that the contemplation of the light-

ing eect would cause, if we manage to abstract ourselves

from the excessive current electric lighting, very far from

the lighting designed by the creators of the chapel, we can

imagine the great expressiveness that would be achieved.

The darkness inning in this cathedral space at dusk would

intensify the beam of light that penetrated through the oc-

The choir stalls of Burgos Cathedral were made by Felipe Bigar-

ny and his workshop in the 1

third of the 16

century.

Fig. 12. Detail of a backrest of the choir stalls of Burgos Cathedral

in which the sun’s ray can be seen penetrating a room

through an oculus and reaching the figure of the Virgin

at the moment of the Annunciation (photo by J.A. Gárate Alcalde)

Il. 12. Fragment oparcia stalli chóru katedry w Burgos,

na którym widać promień słońca wpadający do pomieszczenia

przez okulus i docierający do postaci Matki Boskiej

w chwili Zwiastowania (fot. J.A. Gárate Alcalde)

ulus. This, in its route through the altarpiece, would make

the polychrome and gilding of the illuminated sculptural

elements shine, making them stand out powerfully from

the rest. In turn, the colouring of the vault, with the plinth

probably painted in azure and the ribs and fringes that

sprout from them gilded would further increase the visual

impact of the phenomenon. And all this, surely, coinciding

with the oce of vespers, which is known to have been

celebrated in the chapel since its foundation

Translated by

Malcolm Hayes

Historical Archive of the Burgos Cathedral, ACA 52, fols. 11v–18.

34 Ezequiel Uson Guardiola, José Antonio Gárate Alcalde, Víctor Jørgensen-Mínguez, Eva Espuny Camacho

Graitec Archiwizard Software. Accessed April 15, 2025. http://www.7Fr.

Graitec.com/archiwizard/software/

Hughes, Barnabas, ed. Fibonacci’s De Practica Geometrie. Springer,

2008.

Ibáñez Pérez, Alberto C., and René Jesus Payo Hernanz. Del Gótico al

Renacimiento: Artistas burgaleses entre 1450 y 1600. Caja Círculo,

2008.

Incerti, Manuela. “Astronomical Knowledge in the Sacred Architec-

ture of the Middle Ages in Italy.” Nexus Network Journal 15, no. 3

(2013): 503–26. https://doi.org/10.1007/s00004-013-0167-3.

Incerti, Manuela. “Light-Shadow Interactions in Italian Medieval

Churches.” In Handbook of Archaeoastronomy and Ethnoastron-

omy, edited by Clive L.N. Ruggles, Springer, 2015. https://doi.

org/10.1007/978-1-4614-6141-8_178.

Justi, Carl. “Los maestros de Colonia en la Catedral de Burgos.” Estu-

dios de Arte Español. La España Moderna, 1913.

Martínez-Sanz, Manuel. “Historia del templo catedral de Burgos: escrita

con arreglo a documentos de su archivo.” Imprenta de don Anselmo

Revilla, 1866.

McCluskey, Stephen C. “Astronomies and Rituals at the Dawn of the

Middle Ages.” In Astronomies and Cultures, edited by Clive L.N.

Ruggles and Nicholas J. Saunders. Ocarina book, 1993.

Menéndez-González, Nicolás. “Juan de Colonia en los inicios del Tardo

gótico burgalés.” In Actas del IV Simposio Internacional de Jóvenes

Medievalistas. Murcia, 2009.

Menéndez-González, Nicolás. “Los Colonia en la catedral de Burgos:

Nuevos datos para la historia del templo en los siglos XV y XVI.”

In El mundo de las catedrales. Pasado, presente y futuro. Actas del

Congreso Internacional VIII Centenario Catedral de Burgos. Fun-

dación VIII Centenario de la Catedral de Burgos, 2022.

Meteonorm 8. Accessed April 15, 2024. http://www.meteonorm8.com/en/

Nieto-Alcaide, Victor. La luz, símbolo y sistema visual: El espacio y la

luz en el arte gótico y del Renacimiento. Cuadernos Arte Cátedra,

1989.

Payo-Hernanz, René J., and José Matesanz del Barrio. La Edad de Oro

de la Caput Castellae: Arte y sociedad en Burgos, 1450–1600. Do-

ssoles, 2015.

Sánchez-Ameijeiras, Rocío. “La portada del Sarmental de la catedral de

Burgos: Fuentes y fortuna.” Matèria. Revista Internacional d’Art 1

(2001): 161–98.

SketchUp. Accessed April 15, 2024. http://www.sketchUp/software/.

Uson-Guardiola, Ezequiel. “Deciphering the Greek Temple: Verication

with Software Tools of the Solar Design of the Parthenon in Athens

and the Temple of Zeus in Olympia.” European Journal of Archi-

tecture and Urban Planning 2, no. 1 (2023): 9–18. http://dx.doi.

org/10.24018/ejarch.2023.2.1.19.

Vilas-Estévez, Benito, Ruth Varela, and A. Cesar González-García.

“Previous Tradition? Coinciden`ce? Design? How It Was Possible

to Create the Illumination Eects at the Cathedral of Saint James

(Galicia, Spain)?” Mediterranean Archaeology and Archaeometry

18, no. 4 (2018): 251–8. http://doi.org//10.5281/zenodo.1478696.

Yarza-Luaces, Joaquín. Gil Siloé: El retablo de la Concepción en la

capilla del obispo Acuña. Asociación de Amigos de la Catedral de

Burgos, 2000.

Streszczenie

Ukryta historia katedry w Burgos (Hiszpania): wirtualna rekonstrukcja efektów świetlnych

wygenerowanych w XV-wiecznej kaplicy Poczęcia NMP lub św. Anny

Specjalne efekty świetlne, popularnie zwane „cudami światła”, pojawiają się podczas przesileń lub równonocy w trzech średniowiecznych kościo-

łach zlokalizowanych w hiszpańskim mieście Burgos i jego okolicach. Te hierofanie można zaobserwować w budynkach sakralnych, których projekt

i konstrukcja zostały wykonane przez średniowiecznych architektów związanych z tak zwanym „taller de los Colonia”. Założeniem leżącym u podstaw

badań jest to, że te same efekty zostały wygenerowane również w kaplicy Poczęcia NMP w katedrze w Burgos i były widoczne do czasu zbudowania

kaplicy św. Tekli w XVIII w. W niniejszym artykule wirtualnie odtworzono te efekty świetlne przy użyciu oprogramowania do symulacji oświetlenia

słonecznego i zanalizowano metody ich generowania.

Słowa kluczowe: efekty świetlne, warsztat Juana de Colonia, katedra w Burgos, kaplica Poczęcia NMP, oprogramowanie do symulacji oświetlenia

słonecznego