Cathedral of Saint Mary of the Flower
Cattedrale di Santa Maria del Fiore (Italian)
Cathedral Sanctae Mariae Floris (Latin)
|Province||Archdiocese of Florence|
|Ecclesiastical or organizational status||Cathedral, Minor basilica|
Arnolfo di Cambio
|Length||153 metres (502 ft)|
|Height (max)||114.5 metres (376 ft)|
The Cattedrale di Santa Maria del Fiore (English, "Cathedral of Saint Mary of the Flowers") is the main church of Florence, Italy. Il Duomo di Firenze, as it is ordinarily called, was begun in 1296 in the Gothic style with the design of Arnolfo di Cambio and completed structurally in 1436 with the dome engineered by Filippo Brunelleschi. The exterior of the basilica is faced with polychrome marble panels in various shades of green and pink bordered by white and has an elaborate 19th-century Gothic Revival façade by Emilio De Fabris.
The cathedral complex, located in Piazza del Duomo, includes the Baptistery and Giotto's Campanile. These three buildings are part of the UNESCO World Heritage Site covering the historic centre of Florence and are a major attraction to tourists visiting Tuscany. The basilica is one of Italy's largest churches, and until development of new structural materials in the modern era, the dome was the largest in the world. It remains the largest brick dome ever constructed.
- History 1
- Plan and structure 2.1
- Dome 2.2
- Façade 2.3
- Main Portal 3
- Interior 4
- Crypt 5
- Other burials 6
- See also 7
- Notes 8
- References 9
- Further reading 10
- External links 11
Santa Maria del Fiore was built on the site of an earlier cathedral dedicated to Saint Reparata. The ancient structure, founded in the early 5th century and having undergone many repairs, was crumbling with age, according to the 14th-century Nuova Cronica of Giovanni Villani, and was no longer large enough to serve the growing population of the city. Other major Tuscan cities had undertaken ambitious reconstructions of their cathedrals during the Late Medieval period, such as Pisa and particularly Siena where the enormous proposed extensions were never completed.
The new church was designed by Arnolfo di Cambio and approved by city council in 1294. Di Cambio was also architect of the church of Santa Croce and the Palazzo Vecchio. He designed three wide naves ending under the octagonal dome, with the middle nave covering the area of Santa Reparata. The first stone was laid on September 9, 1296, by Cardinal Valeriana, the first papal legate ever sent to Florence. The building of this vast project was to last 140 years; Arnolfo's plan for the eastern end, although maintained in concept, was greatly expanded in size.
After Arnolfo died in 1310, work on the cathedral slowed for thirty years. When the relics of Saint Zenobius were discovered in 1330 in Santa Reparata, the project gained a new impetus. In 1331, the Arte della Lana, the guild of wool merchants, took over patronage for the construction of the cathedral and in 1334 appointed Giotto to oversee the work. Assisted by Andrea Pisano, Giotto continued di Cambio's design. His major accomplishment was the building of the campanile. When Giotto died in 1337, Andrea Pisano continued the building until work was halted due to the Black Death in 1348.
In 1349, work resumed on the cathedral under a series of architects, starting with Francesco Talenti, who finished the campanile and enlarged the overall project to include the apse and the side chapels. In 1359, Talenti was succeeded by Giovanni di Lapo Ghini (1360–1369) who divided the center nave in four square bays. Other architects were Alberto Arnoldi, Giovanni d'Ambrogio, Neri di Fioravante and Andrea Orcagna. By 1375, the old church Santa Reparata was pulled down. The nave was finished by 1380, and by 1418, only the dome remained incomplete.
On 18 August 1418, the Arte della Lana announced an architectural design competition for erecting Neri's dome. The two main competitors were two master goldsmiths, Lorenzo Ghiberti and Filippo Brunelleschi, the latter of whom was supported by Cosimo de Medici. Ghiberti had been the winner of a competition for a pair of bronze doors for the Baptistery in 1401 and lifelong competition between the two remained sharp. Brunelleschi won and received the commission.
Ghiberti, appointed coadjutator, drew a salary equal to Brunelleschi's and, though neither was awarded the announced prize of 200 florins, was promised equal credit, although he spent most of his time on other projects. When Brunelleschi became ill, or feigned illness, the project was briefly in the hands of Ghiberti. But Ghiberti soon had to admit that the whole project was beyond him. In 1423, Brunelleschi was back in charge and took over sole responsibility.
Work started on the dome in 1420 and was completed in 1436. The cathedral was consecrated by Pope Eugene IV on March 25, 1436, (the first day of the year according to the Florentine calendar). It was the first 'octagonal' dome in history to be built without a temporary wooden supporting frame. It was one of the most impressive projects of the Renaissance. During the consecration in 1436, Guillaume Dufay's motet Nuper rosarum flores was performed. The structure of this motet was strongly influenced by the structure of the dome.
The decoration of the exterior of the cathedral, begun in the 14th century, was not completed until 1887, when the polychrome marble façade was completed with the design of Emilio De Fabris. The floor of the church was relaid in marble tiles in the 16th century.
The exterior walls are faced in alternate vertical and horizontal bands of polychrome marble from Carrara (white), Prato (green), Siena (red), Lavenza and a few other places. These marble bands had to repeat the already existing bands on the walls of the earlier adjacent baptistery the Battistero di San Giovanni and Giotto's Bell Tower. There are two side doors: the Doors of the Canonici (south side) and the Door of the Mandorla (north side) with sculptures by Nanni di Banco, Donatello, and Jacopo della Quercia. The six side windows, notable for their delicate tracery and ornaments, are separated by pilasters. Only the four windows closest to the transept admit light; the other two are merely ornamental. The clerestory windows are round, a common feature in Italian Gothic.
During its long history, this cathedral has been the seat of the Council of Florence (1439), heard the preachings of Girolamo Savonarola and witnessed the murder of Giuliano di Piero de' Medici on Sunday, 26 April 1478 (with Lorenzo Il Magnifico barely escaping death), in the Pazzi conspiracy.
Plan and structure
The cathedral of Florence is built as a basilica, having a wide central nave of four square bays, with an aisle on either side. The chancel and transepts are of identical polygonal plan, separated by two smaller polygonal chapels. The whole plan forms a Latin cross. The nave and aisles are separated by wide pointed Gothic arches resting on composite piers.
The dimensions of the building are enormous: building area 8,300 square meters, length 153 metres (502 ft), width 38 metres (124 ft), width at the crossing 90 metres (295 ft). The height of the arches in the aisles is 23 metres (75 ft). The height of the dome is 114.5 m.
By the beginning of the 15th century, after a hundred years of construction, the structure was still missing its dome. The basic features of the dome had been designed by Arnolfo di Cambio in 1296. His brick model, 4.6 metres (15 ft) high, 9.2 metres (30 ft) long, was standing in a side aisle of the unfinished building, and had long been sacrosanct. It called for an octagonal dome higher and wider than any that had ever been built, with no external buttresses to keep it from spreading and falling under its own weight.
|Smarthistory - Brunelleschi's Dome|
The commitment to reject traditional Gothic buttresses had been made when Neri di Fioravanti's model was chosen over a competing one by Giovanni di Lapo Ghini. That architectural choice, in 1367, was one of the first events of the Italian Renaissance, marking a break with the Medieval Gothic style and a return to the classic Mediterranean dome. Italian architects regarded Gothic flying buttresses as ugly makeshifts. Furthermore, the use of buttresses was forbidden in Florence, as the style was favored by central Italy's traditional enemies to the north. Neri's model depicted a massive inner dome, open at the top to admit light, like Rome's Pantheon, but enclosed in a thinner outer shell, partly supported by the inner dome, to keep out the weather. It was to stand on an unbuttressed octagonal drum. Neri's dome would need an internal defense against spreading (hoop stress), but none had yet been designed.
The building of such a masonry dome posed many technical problems. Brunelleschi looked to the great dome of the
- Official website
- L'Opera del Duomo, Firenze
- Brunelleschi's Dome - en
- "The Cathedral". The Florence Art Guide. 2004. Retrieved July 14, 2006.
- Museums in Florence - Cathedral and Giotto Belltower
- Horner, Susan; Horner, Joanna (December 27, 2005). "Chapter III: The Cathedral - Exterior". Walks in Florence. Retrieved July 14, 2006.
- NGM.NationalGeographic.com 2014- 02 Il Duomo 360 Panorama View Interactive
- NGM.NationalGeographic.com 2014-02 Il Duomo Cutaway Interactive
- ngm.nationalgeographic.com 2014-02 ll Duomo Piazza 360 degree panorama interactive
- ngm.nationalgeographic.com 2014-02 Il Duomo Compared to other Domes Interactive
- "The Great Cathedral Mystery", PBS Nova TV documentary, February 12, 2014
- Hunt, Don, "Secrets of the Duomo", Journal, Issue 2, 2014, International Union of Bricklayers and Allied Craftworkers
- Mueller, Tom, "Brunelleschi’s Dome: How did a hot-tempered goldsmith with no formal architectural training create the most miraculous edifice of the Renaissance?", National Geographic magazine, February 2014
- Ricci, Massimo, Il genio di Brunelleschi e la costruzione della Cupola di Santa Maria del Fiore, Livorno : Casa Editrice Sillabe S.r.l., April 2014. (The genius of Filippo Brunelleschi and the construction of the dome of Santa Maria del Fiore). ISBN 978-88-8347-691-4. The book is the result of forty years of research on the secret technique with which Brunelleschi built the Dome of Santa Maria del Fiore in Florence. Ricci makes the case for the dome being an inverted arch and uses a herringbone pattern (spina a pesce) for the dome's bricks.
- Vereycken, Karel, "The Secrets of the Florentine Dome", Schiller Institute, 2013. (Translation from the French, "Les secrets du dôme de Florence", la revue Fusion, n° 96, Mai, Juin 2003)
- Bartlett, Kenneth R. (1992). The Civilization of the Italian Renaissance. Toronto: D.C. Heath and Company. ISBN 0-669-20900-7 (Paperback).
- King, Ross (2000). Brunelleschi’s Dome: How a Renaissance Genius Reinvented Architecture. London: Chatto & Windus.
- Jepson, Tim (2001). The National Geographic Traveler, Florence & Tuscany.
- Henry A. Millon (ed.) (1994). Italian Renaissance Architecture: from Brunelleschi to Michelangelo. London:
- Montrésor, Carlo (2000). The Opera del Duomo, Museum in Florence.
- Suro, Roberto (July 28, 1987). "Cracks in a Great Dome in Florence May Point to Impending Disaster". New York Times: C3. Retrieved 2010-02-26.
- Tacconi, Marica S. Cathedral and Civic Ritual in Late Medieval and Renaissance Florence: The Service Books of Santa Maria del Fiore. Cambridge: Cambridge University Press, 2005. ISBN 978-0-521-81704-2
- Wirtz, Rolf C. Kunst & Architektur, Florenz.
- Cupola di Santa Maria del Fiore: il cantiere di restauro 1980-1995, a cura di Cristina Acidini Luchinat e Riccardo Dalla Negra. Istituto poligrafico e Zecca dello Stato (Roma). 1995. Library of Congress permalink
- Devémy, Jean-François (2013). Sur les traces de Filippo Brunelleschi, l'invention de la coupole de Santa Maria del Fiore à Florence. Suresnes: Les Editions du Net. (in line presentation)
- Gärtner, Peter J. (1998). Filippo Brunelleschi 1377-1446. Köln : Könemann.
- Bartlett, pp. 36–37; according to Bartlett, the people of Florence continued to call the cathedral by its former name for some time after reconstruction.
- Barlett, 36.
- Zucconi, Guido (1995). Florence: An Architectural Guide. San Giovanni Lupatoto, Vr, Italy: Arsenale Editrice srl.
- King, pp. 76–79.
- "Santa Maria Del Fiore Church (Dome) Firenze Italy". En.firenze-online.com. Retrieved 2013-03-26.
- King, p. 10
- "Brunelleschi's Dome". Smarthistory at Khan Academy. Retrieved December 19, 2012.
- King, p. 9.
- King, p. 7.
- PBS' The Medici: Godfathers of the Renaissance, Birth of a Dynasty (see http://www.youtube.com/watch?v=9FFDJK8jmms at the 20:15 mark)
- Stevenson, Niel (2007) Architecture Explained. ISBN 0756628687. pp. 36–37.
- King, pp. 70–73.
- King, p. 97.
- Mueller, Tom (February 10, 2014). "Mystery of Florence's Cathedral Dome May Be Solved". National Geographic Society. Retrieved 31 December 2014.
- NationalGeographic.com 2014-02 Il Duomo Tom Mueller
- NationalGeographic.com 2014-02 Il Doumo Design Video
- King, pp. 105-107.
- Gartner, Peter, Filippo Brunelleschi 1377-1446, p 95.
- King, p. 69.
- Paolo Galluzzi, "Leonard de Vinci, engineer and architect",p. 50
- Figures vary. archINFORM gives a 45 m wide tambour, while Santa Maria del Fiore at Structurae gives a 43 m diameter of the cupola, others as little as 42 m.
- As referenced in "Cupola di Santa Maria del Fiore: il cantiere di restauro 1980-1995", a cura di Cristina Acidini Luchinat e Riccardo Dalla Negra published by Istituto Poligrafico e Zecca dello Stato (Roma) in 1995 (ISBN 8824039561)
- Thesaurus Florentinus project page (in Italian), Soprintendenza ai Beni Architettonici e Paesaggisitici di Firenze, Ministero dei Beni Culturali
- Roman Catholic Marian churches
- List of largest domes in the world
- Santa Reparata, Florence
- Inferno (Dan Brown novel)
- History of Medieval Arabic and Western European domes
- Zenobius of Florence
- Giovanni Benelli
- Filippo Brunelleschi
- Giotto di Bondone
- Pope Nicholas II
- Pope Stephen IX
- John Hawkwood
Also buried in the former cathedral of Santa Reparata was Conrad II of Italy but his wife was laid down to rest with him.
The archaeological history of this huge area was reconstructed through the work of Dr. Franklin Toker: remains of Roman houses, an early Christian pavement, ruins of the former cathedral of Santa Reparata and successive enlargements of this church. Close to the entrance, in the part of the crypt open to the public, is the tomb of Brunelleschi. While its location is prominent, the actual tomb is simple and humble. That the architect was permitted such a prestigious burial place is proof of the high esteem he was given by the Florentines.
The cathedral underwent difficult excavations between 1965 and 1974. The subterranean vaults were used for the burial of Florentine bishops throughout the centuries.
It was suggested that the interior of the 45 metre (147 ft) wide dome should be covered with a mosaic decoration to make the most of the available light coming through the circular windows of the drum and through the lantern. Brunelleschi had proposed the vault to glimmer with resplendent gold, but his death in 1446 put an end to this project, and the walls of the dome were whitewashed. Grand Duke Federico Zuccari and would last till 1579. The upper portion, near the lantern, representing The 24 Elders of Apoc. 4 was finished by Vasari before his death in 1574. Federico Zuccari and a number of collaborators, such as Domenico Cresti, finished the other portions: (from top to bottom) Choirs of Angels; Christ, Mary and Saints; Virtues, Gifts of the Holy Spirit and Beatitudes; and at the bottom of the cuppola: Capital Sins and Hell. These frescoes are considered Zuccari's greatest work. But the quality of the work is uneven because of the input of different artists and the different techniques. Vasari had used true fresco, while Zuccari had painted in secco. During the restoration work ended in 1995, the entire pictorial cycle of the The Last Judgment was photographed with specially designed equipment and all the information collected in a catalogue. All the restoration information along with reconstructed images of the frescos were stored and managed in the Thesaurus Florentinus computer system.
Many decorations date from the 16th-century patronage of the Grand Dukes, such as the pavement in colored marble, attributed to Baccio d'Agnolo and Francesco da Sangallo (1520–26). Some pieces of marble from the façade were used, topside down, in the flooring (as was shown by the restoration of the floor after the 1966 flooding).
In the back of the middle of the three apses is the altar of Saint Zanobius, first bishop of Florence. Its silver shrine, a masterpiece of Ghiberti, contains the urn with his relics. The central compartment shows us one his miracles, the reviving of a dead child. Above this shrine is the painting Last Supper by the lesser-known Giovanni Balducci. There was also a glass-paste mosaic panel The Bust of Saint Zanobius by the 16th-century miniaturist Monte di Giovanni, but it is now on display in the Museum Opera del Duomo.
The monumental crucifix, behind the Bishop's Chair at the high altar, is by Benedetto da Maiano (1495–1497). The choir enclosure is the work of the famous Bartolommeo Bandinelli. The ten-paneled bronze doors of the sacristy were made by Luca della Robbia, who has also two glazed terracotta works inside the sacristy: Angel with Candlestick and Resurrection of Christ.
The beautiful funeral monument of Antonio d'Orso (1323), bishop of Florence, was made by Tino da Camaino, the most important funeral sculptor of his time.
Donatello designed the stained-glass window (Coronation of the Virgin) in the drum of the dome (the only one that can be seen from the nave).
Christ crowning Mary as Queen, the stained-glass circular window above the clock, with a rich range of coloring, was designed by Gaddo Gaddi in the early 14th century.
The church is particularly notable for its 44 stained glass windows, the largest undertaking of this kind in Italy in the 14th and 15th century. The windows in the aisles and in the transept depict saints from the Old and the New Testament, while the circular windows in the drum of the dome or above the entrance depict Christ and Mary. They are the work of the greatest Florentine artists of their times, such as Donatello, Lorenzo Ghiberti, Paolo Uccello and Andrea del Castagno.
Above the main door is the colossal clock face with fresco portraits of four Prophets or Evangelists by Paolo Uccello (1443). This one-handed liturgical clock shows the 24 hours of the hora italica (Italian time), a period of time ending with sunset at 24 hours. This timetable was used until the 18th century. This is one of the few clocks from that time that still exist and are in working order.
- Dante Before the City of Florence by Domenico di Michelino (1465). This painting is especially interesting because it shows us, apart from scenes of the Divine Comedy, a view on Florence in 1465, a Florence such as Dante himself could not have seen in his time.
- Funerary Monument to Sir John Hawkwood by Paolo Uccello (1436). This almost monochrome fresco, transferred to canvas in the 19th century, is painted in terra verde, a color closest to the patina of bronze.
- Equestrian statue of Niccolò da Tolentino by Andrea del Castagno (1456). This fresco, transferred on canvas in the 19th century, in the same style as the previous one, is painted in a color resembling marble. However, it is more richly decorated and gives more the impression of movement. Both frescoes portray the condottieri as heroic figures riding triumphantly. Both painters had problems when applying in painting the new rules of perspective to foreshortening: they used two unifying points, one for the horse and one for the pedestal, instead a single unifying point.
- Busts of Giotto (by Benedetto da Maiano), Brunelleschi (by Buggiano - 1447), Marsilio Ficino, and Antonio Squarcialupi (a most famous organist). These busts all date from the 15th and the 16th centuries.
As this cathedral was built with funds from the public, some important works of art in this church honour illustrious men and military leaders of Florence:
Many decorations in the church have been lost in the course of time, or have been transferred to the Museum Opera del Duomo, such as the magnificent cantorial pulpits (the singing galleries for the choristers) of Luca della Robbia and Donatello.
The Gothic interior is vast and gives an empty impression. The relative bareness of the church corresponds with the austerity of religious life, as preached by Girolamo Savonarola.
On top of the façade is a series of niches with the twelve Apostles with, in the middle, the Madonna with Child. Between the rose window and the tympanum, there is a gallery with busts of great Florentine artists.
The three huge bronze doors date from 1899 to 1903. They are adorned with scenes from the life of the Madonna. The mosaics in the lunettes above the doors were designed by Niccolò Barabino. They represent (from left to right): Charity among the founders of Florentine philanthropic institutions; Christ enthroned with Mary and John the Baptist; and Florentine artisans, merchants and humanists. The pediment above the central portal contains a half-relief by Tito Sarrocchi of Mary enthroned holding a flowered scepter. Giuseppe Cassioli sculpted the right-hand door.
The whole façade is dedicated to the Mother of Christ.
In 1864, a competition held to design a new façade was won by Emilio De Fabris (1808–1883) in 1871. Work began in 1876 and was completed in 1887. This neo-gothic façade in white, green and red marble forms a harmonious entity with the cathedral, Giotto's bell tower and the Baptistery, but some think it is excessively decorated.
The original façade, designed by Arnolfo di Cambio and usually attributed to Giotto, was actually begun twenty years after Giotto's death. A mid-15th-century pen-and-ink drawing of this so-called Giotto's façade is visible in the Codex Rustici, and in the drawing of Bernardino Poccetti in vain. While the Bernaducio Compact stated clearly on section 98:46 "Id Vitium Nulli per sauculeas longa notatum," a defined proverb in Otis' Metamorpheses, it should be known that remedies can further pontificate this conjecture.
The building of the cathedral had started in 1296 with the design of Arnolfo di Cambio and was completed in 1469 with the placing of Verrochio's copper ball atop the lantern. But the façade was still unfinished and would remain so until the 19th century.
A huge statue of Brunelleschi now sits outside the Palazzo dei Canonici in the Piazza del Duomo, looking thoughtfully up towards his greatest achievement, the dome that would forever dominate the panorama of Florence. It is still the largest masonry dome in the world.
Leonardo might have also participated in the design of the bronze ball, as stated in the G manuscript of Paris "Remember the way we soldered the ball of Santa Maria del Fiore".
The commission for this bronze ball [atop the lantern] went to the sculptor Andrea del Verrocchio, in whose workshop there was at this time a young apprentice named Leonardo da Vinci. Fascinated by Filippo's [Brunelleschi's] machines, which Verrocchio used to hoist the ball, Leonardo made a series of sketches of them and, as a result, is often given credit for their invention.
Brunelleschi's ability to crown the dome with a lantern was questioned and he had to undergo another competition, even though there had been evidence that Brunelleschi had been working on a design for a lantern for the upper part of the dome. The evidence is shown in the curvature, which was made steeper than the original model. He was declared the winner over his competitors Lorenzo Ghiberti and Antonio Ciaccheri. His design (now on display in the Museum Opera del Duomo) was for an octagonal lantern with eight radiating buttresses and eight high arched windows. Construction of the lantern was begun a few months before his death in 1446. Then, for 15 years, little progress was possible, due to alterations by several architects. The lantern was finally completed by Brunelleschi's friend Michelozzo in 1461. The conical roof was crowned with a gilt copper ball and cross, containing holy relics, by Verrocchio in 1469. This brings the total height of the dome and lantern to 114.5 meters (375 ft). This copper ball was struck by lightning on 17 July 1600 and fell down. It was replaced by an even larger one two years later.
A modern understanding of physical laws and the mathematical tools for calculating stresses were centuries in the future. Brunelleschi, like all cathedral builders, had to rely on intuition and whatever he could learn from the large scale models he built. To lift 37,000 tons of material, including over 4 million bricks, he invented hoisting machines and lewissons for hoisting large stones. These specially designed machines and his structural innovations were Brunelleschi's chief contribution to architecture. Although he was executing an aesthetic plan made half a century earlier, it is his name, rather than Neri's, that is commonly associated with the dome.
The outer dome was not thick enough to contain embedded horizontal circles, being only 60 centimetres (2 ft) thick at the base and 30 centimetres (1 ft) thick at the top. To create such circles, Brunelleschi thickened the outer dome at the inside of its corners at nine different elevations, creating nine masonry rings, which can be observed today from the space between the two domes. To counteract hoop stress, the outer dome relies entirely on its attachment to the inner dome and has no embedded chains.
A circular masonry dome can be built without supports, called centering, because each course of bricks is a horizontal arch that resists compression. In Florence, the octagonal inner dome was thick enough for an imaginary circle to be embedded in it at each level, a feature that would hold the dome up eventually, but could not hold the bricks in place while the mortar was still wet. Brunelleschi used a herringbone brick pattern to transfer the weight of the freshly laid bricks to the nearest vertical ribs of the non-circular dome.
Each of Brunelleschi's stone chains was built like an octagonal railroad track with parallel rails and cross ties, all made of sandstone beams 43 centimetres (17 in) in diameter and no more than 2.3 metres (7.5 ft) long. The rails were connected end-to-end with lead-glazed iron splices. The cross ties and rails were notched together and then covered with the bricks and mortar of the inner dome. The cross ties of the bottom chain can be seen protruding from the drum at the base of the dome. The others are hidden. Each stone chain was supposed to be reinforced with a standard iron chain made of interlocking links, but a magnetic survey conducted in the 1970s failed to detect any evidence of iron chains, which if they exist are deeply embedded in the thick masonry walls. Brunelleschi also included vertical "ribs" set on the corners of the octagon, curving towards the center point. The Ribs, 13 feet (4 meters) deep, are supported by 16 concealed ribs radiating from center. The ribs had slits to take beams that supported platforms, thus allowing the work to progress upward without the need for scaffolding.
Brunelleschi's solutions were ingenious. The spreading problem was solved by a set of four internal horizontal stone and iron chains, serving as barrel hoops, embedded within the inner dome: one at the top, one at the bottom, with the remaining two evenly spaced between them. A fifth chain, made of wood, was placed between the first and second of the stone chains. Since the dome was octagonal rather than round, a simple chain, squeezing the dome like a barrel hoop, would have put all its pressure on the eight corners of the dome. The chains needed to be rigid octagons, stiff enough to hold their shape, so as not to deform the dome as they held it together.
. The model served as a guide for the craftsmen, but was intentionally incomplete, so as to ensure Brunelleschi's control over the construction. Museo dell'Opera del Duomo and Nanni di Banco, a model which is still displayed in the Donatello Brunelleschi chose to follow such design and employed a double shell, made of sandstone and marble. Brunelleschi would have to build the dome out of brick, due to its light weight compared to stone and being easier to form, and with nothing under it during construction. To illustrate his proposed structural plan, he constructed a wooden and brick model with the help of