Arabic and Western-European Domes
Seventeen years after the last Western Roman Emperor was deposed, Theodoric the Great was the Ostrogothic king of Italy. His building projects largely continued existing architectural conventions. His Arian Baptistry in Ravenna (c. 500), for example, closely echoes the Baptistry of Neon built before it. Both baptistries are octagonal buildings with pyramidal roofs concealing interior domes.
The Mausoleum of Theodoric, however, was understood by contemporaries to be remarkable. Begun in 520, the 36-foot-wide (11 m) dome over the mausoleum was carved out of a single 440 ton slab of limestone and positioned some time between 522 and 526. The twelve brackets carved as part of the dome's exterior are thought to have been used to maneuver the piece into place. The choice of large limestone blocks for the structure is significant as the most common construction material in the West at that time was brick. It is likely that foreign artisans were brought to Ravenna to build the structure; possibly from Syria, where such stonework was used in contemporary buildings.
The Syria and Palestine area has a long tradition of domical architecture, including wooden domes in shapes described as "conoid", or similar to pine cones. When the Arab Muslim forces conquered the region, they employed local craftsmen for their buildings and, by the end of the 7th century, the dome had begun to become an architectural symbol of Islam. The rapidity of this adoption was likely aided by the Arab religious traditions, which predate Islam, of both domed structures to cover the burial places of ancestors and the use of a round tabernacle tent with a dome-like top made of red leather for housing idols.
The Dome of the Rock in Jerusalem, the earliest surviving Islamic building, was completed in 691 by Umayyad caliph Abd Al-Malik. Its design was that of a ciborium, or reliquary, such as those common to Byzantine martyria and the major Christian churches of the city. The dome, a double shell design made of wood, is 20.44 meters in diameter and 30 meters high. It is currently covered in gilded aluminum. Several restorations since 1958 to address structural damage have resulted in the extensive replacement of tiles, mosaics, ceilings, and walls such that "nearly everything that one sees in this marvelous building was put there in the second half of the twentieth century", but without significant change to its original form and structure.
Byzantine workmen built the Umayyad Mosque of Damascus and its hemispherical dome for Sherif al Walid in 705. The dome rests upon an octagonal base formed by squinches.
Italian church architecture from the late sixth century to the end of the eighth century is influenced less by the trends of Constantinople than by a variety of Eastern provincial plans. With the crowning of Charlemagne as a new Roman Emperor, these influences were largely replaced in a revival of earlier Western building traditions. Occasional exceptions include examples of early quincunx churches at Milan and near Cassino.
Charlemagne built the Palatine Chapel at his palace at Aachen between 789 and its consecration in 805. The architect is thought to be Odo of Metz, although the quality of the ashlar construction has led to speculation about the work of outside masons. The chapel's domed octagon design was influenced by Byzantine models such as the Basilica of San Vitale in Ravenna, the Church of Sergius and Bacchus in Constantinople, and perhaps the Chrysotriklinos, or "golden reception hall", of the Great Palace of Constantinople. The octagonal domical vault measures 16.5 meters wide and 38 meters high. It was the largest dome north of the Alps at that time.
The dome of the Great Mosque of Kairouan (also called the Mosque of Uqba) built in the first half of the 9th century, has a ribbed hemispherical dome which rests on an octogonal drum with slightly concave sides.
The Great Mosque of Córdoba, begun in 785 under the last of the Umayyad caliphs, was enlarged by Al-Hakam II between 961 and 976 to include four domes and a remodeled mihrab. The central dome, in front of the mihrab area, transitions from a square bay with decorative squinches to eight overlapping and intersecting arches which surround and support a scalloped dome.
Southern Italy, Sicily, and Venice served as outposts of Middle Byzantine architectural influence in Italy. That southern Italy was reconquered and ruled by a Byzantine governor from about 970 to 1071 explains the relatively large number of small and rustic Middle Byzantine-style churches found there, including the Cattolica in Stilo and S. Marco in Rossano. Both are cross-in-square churches with five small domes on drums in a quincunx pattern and date either to the period of Byzantine rule or after.
The church architecture of Sicily has fewer examples, having been conquered by Muslims in 827, but quincunx churches exist with single domes on tall central drums and either Byzantine pendentives or Islamic squinches. Very little architecture from the Islamic period survives on the island. The domed basilicas built in Sicily after the Norman Conquest of 1091, however, incorporate distinctly Islamic architectural elements. They include hemispherical domes positioned directly in front of apses, similar to the common positioning in mosques of domes directly in front of mihrabs, and the domes use squinches supported on four points, as do the domes of Islamic North Africa and Egypt. In other cases, domes with tall drums, engaged columns, and blind arcades exhibit Byzantine influences.
Venice's close mercantile links to the Byzantine empire resulted in the architecture of that city and its vicinity being a blend of Byzantine and northern Italian influences, although nothing from the ninth and tenth centuries has survived except for the foundations of the first St. Mark's Basilica. The current St Mark's Basilica was built between 1063 and 1072, replacing an earlier church while replicating its Greek cross plan. Five domes vault the interior (one each over the four arms of the cross and one in the center). These domes were built in the Byzantine style, in imitation of the now lost Church of the Holy Apostles in Constantinople. Mounted over pendentives, each dome has a ring of windows at its base. Much higher wooden outer domes with lead roofing and cupolas were added between 1210 and 1270, allowing the church to be seen from a great distance. In addition to allowing for a more imposing exterior, building two distinct shells in a dome improved weather protection. However, it was a rare practice before the 11th century.
Domes in Romanesque architecture are generally found within crossing towers at the intersection of a church's nave and transept, which conceal the domes externally. The precise form of these differ from region to region. Romanesque domes are typically octagonal in plan, possibly due to their use of corner squinches to translate a square bay into a suitable octagonal base. They appear "in connection with basilicas almost throughout Europe" between 1050 and 1100.
Being a part of the Holy Roman Empire, the architecture of northern Italy developed differently than the rest of the Italian peninsula, especially after 1100. Churches were designed with vaulting from the outset, rather than as colonnaded basilicas with timber roofs, and many have octagonal domes with squinches over their crossings or choirs.
The earliest use of the octagonal cloister vault within an external housing at the crossing of a cruciform church may be at Acqui Cathedral in Acqui Terme, Italy, which was completed in 1067. This becomes increasingly popular as a Romanesque feature over the course of the next fifty years. The first Lombard church to have a lantern tower, concealing an octagonal cloister vault, was San Nazaro in Milan, just after 1075. Many other churches followed suit in the next few decades, such as the Basilica of San Michele Maggiore in Pavia and the Basilica of Sant'Ambrogio in Milan.
The renovation of Speyer Cathedral, the largest of the Imperial Cathedrals of the Holy Roman Empire and the burial church of the Salian dynasty, was begun around 1080 by the Emperor Henry IV, soon after he had returned from a trip to Canossa in northern Italy. Although the church had only just been consecrated in 1061, Henry called upon craftsmen from across the empire for its renovation. The redesign included two octagonal cloister vaults within crossing towers, one at the east crossing with an external dwarf gallery and one at the west end. This was very soon imitated elsewhere and became the model for later Rhenish octagonal crossing domes, such as those of Worms Cathedral (c. 1120 - 1181) and Mainz Cathedral (c. 1081 - 1239).
Pisa Cathedral, built between 1063 and 1118, includes a high elliptical dome at the crossing of its nave and transept. The dome was one of the first in Romanesque architecture and is considered the masterpiece of Romanesque domes. Rising 48 meters above a rectangular bay, the shape of the dome was unique at the time. The rectangular bay's dimensions are 18 meters by 13.5 meters. Squinches were used at the corners to create an elongated octagon and corbelling used to create an oval base for the dome. The tambour on which the dome rests dates to between 1090 and 1100, and it is likely that the dome itself was built at this time. There is evidence that the builders did not originally plan for the dome and decided on the novel shape to accommodate the rectangular crossing bay, which would make an octagonal cloister vault very difficult. Additionally, the dome may have originally been covered by a lantern tower which was removed in the 1300s, exposing the dome, to reduce weight on foundations not designed to support it. This would have been done no later than 1383, when the Gothic loggetta on the exterior of the dome was added, along with the buttressing arches on which it rests.
An aspiring competitor to Pisa, the city of Florence took the opposite side in the conflict between Pope and Emperor, siding with the Pope in Rome. This was reflected architecturally in the "proto-renaissance" style of its buildings. The eight-sided Florence Baptistery, with its large octagonal cloister vault beneath a pyramidal roof, was likely built between 1059 and 1128, with the dome and attic built between 1090 and 1128. The lantern above the dome is dated to 1150. It takes inspiration from the Pantheon in Rome for its oculus and much of its interior decoration, although the pointed dome is structurally similar to other Lombard domes, such as that of the later Cremona Baptistery.
The Crusades, beginning in 1095, also appear to have had an impact on domed architecture in Western Europe, particularly in the areas around the Mediterranean Sea. The Dome of the Rock and the Al-Aqsa Mosque on the Temple Mount of Jerusalem were taken to represent the Temple of Solomon and the Palace of Solomon, respectively. The Knights Templar, headquartered at the site, built a series of centrally-planned churches throughout Europe modeled on the Church of the Holy Sepulchre, with the Dome of the Rock also an influence.
Medieval churches in southwest France at Solignac, Souillac, and Périgueux have five domes in a cruciform arrangement similar to that of St. Mark's Basilica. Dozens of other Romanesque churches in the region have a single nave with domed roofs. The earliest may be Angoulême Cathedral, built from 1105 to 1128. Its long nave is covered by four stone domes on pendentives, springing from French pointed arches, the last of which covers the crossing and is surmounted by a stone lantern. Cahors Cathedral (c.1100-1119) covers its nave with two large domes in the same manner and influenced the later building at Souillac. The cathedral of S. Front at Périgueux was built c. 1125-1150. The use of pendentives to support domes in the Aquitaine region, rather than the squinches more typical of western medieval architecture, strongly implies a Byzantine influence. There are also examples of French Romanesque churches with oval plan domes, such as the churches at Saint-Martin-de-Gurson, Dordogne and Balzac, Charente.
During the Reconquista, the Kingdom of León in northern Spain built three churches famous for their domed crossing towers, called "cimborios", as it acquired new territories. The Cathedral of Zamora, the Cathedral of Salamanca, and the collegiate church of Toro were built around the middle of the 12th century. All three buildings have stone umbrella domes with sixteen ribs over windowed drums of either one or two stories, springing from pendentives. All three also have four small round towers engaged externally to the drums of the domes on their diagonal sides. The architectural influences at work here have been much debated, with proposed origins ranging from Jerusalem, Islamic Spain, the Limousin region in western France, or a mixture of sources.
Another unusual Spanish example from the late 12th or early 13th century is the dome of The Church of the Holy Sepulchre in Torres Del Río, on the Way of St. James. The Way, a major pilgrimage route through northern Spain to the reputed burial place of St. James the Greater, attracted pilgrims from throughout Europe, especially after pilgrimage to Jerusalem was cut off. The difficulty of travel to Jerusalem for pilgrimage prompted some new churches to be built as a form of substitute, evoking the central plan and dome of Jerusalem's Church of the Holy Sepulchre with their own variant. The dome in this case, however, is most evocative of the central mihrab dome of the Great Mosque of Cordoba. Over an octagonal room, the stone dome is formed by sixteen ribs, eight of which intersect with one another in a star pattern to define a smaller octagon at the center of the dome.
The domed "Decagon" nave of St. Gereon's Basilica in Cologne, Germany, a ten-sided space in an oval shape, was built between 1219 and 1227 upon the remaining low walls of a 4th century Roman martyrium. The ribbed dome rises four stories and 34.55 meters above the floor, covering an oval area 21 meters long and 16.9 meters wide. It is unique among the twelve Romanesque churches of Cologne, and in European architecture in general, and may have been the largest dome built in this period in Western Europe until the completion of the dome of Florence Cathedral.
Gothic domes are uncommon due to the use of ribbed vaulting, and with the crossing usually focused instead by a tall steeple, but there are examples of small octagonal domes at cathedral crossings as the style developed from Romanesque. Spaces of circular or octagonal plan were sometimes covered with vaults of a "double chevet" style, similar to the chevet apse vaulting in Gothic cathedrals. The crossing of Saint Nicholas at Blois is an example. Timber star vaults such as those over York Minster's octagonal Chapter house (ca. 1286-1296) and the elongated octagon plan of Wells Cathedral's Lady Chapel (ca.1320-1340) imitated much heavier stone vaulting. The wooden vaulting over the crossing of Ely Cathedral in England was built after the original crossing tower collapsed in 1322. It was conceived by Alan of Walsingham and designed by master carpenter William Hurley. Eight hammer vaults extend from eight piers over the 22 meter wide octagonal crossing and meet at the base of a large octagonal lantern, which is covered by a star vault.
Star-shaped domes are also found at the Moorish palace of the Alhambra in Granada, Spain, which contains domed audience halls built to mirror the heavenly constellations. The Hall of the Abencerrajes (c. 1333-1391) and the Hall of the two Sisters (c. 1333-1354) are extraordinarily developed examples of muqarnas domes, taking the tradition of the squinch in Islamic architecture from a functional element in the zone of transition to a highly ornamental covering for the dome itself. The structural elements of these two domes are actually brick vaulting, but these are completely covered by the intricate mocárabe stalactites. The lacy and star-shaped crossing dome of Burgos Cathedral (1567) may have been inspired by these examples, in addition to that built over the cathedral's octagonal Chapel of the Condestable (1482–94) in the Gothic style.
If an external lantern tower was removed from Pisa Cathedral in the 1300s, exposing the dome, one reason may have been to stay current with more recent projects in the region, such as the domed cathedrals of Siena and Florence. The dome of Siena Cathedral had an exposed profile as early as 1224. Set over an irregular 17.7 meter wide hexagon with squinches to form an irregular twelve-sided base, the dome of Siena Cathedral has two shells and was completed in 1264. No large dome had ever before been built over a hexagonal crossing. Rapid progress on a radical expansion of the cathedral which would have involved replacing the existing dome with a larger one was halted not long after the city was struck with an outbreak of the Black Death in 1348. The dome was originally topped with a copper orb, similar to that over Pisa's dome today, but this was replaced in 1385 by a cupola surmounted by a smaller sphere and cross. The current lantern dates from the 17th century and the current outer dome is a 19th century replacement.
It was only a few years after the city of Siena had decided to abandon the massive expansion and redesign of their Cathedral in 1355 that Florence decided to greatly expand theirs. A plan for the dome of Florence Cathedral was settled by 1357. However, in 1368 the plan was altered at the east end to increase the scale of the octagonal dome, widening it from 62 to 72 braccia, with the intent to further surpass the domes of Pisa and Siena. The scale of this new dome was so ambitious that experts for the Opera del Duomo, the board supervising the construction, expressed the opinion as early as 1394 that the dome could not be accomplished. The enlarged dome would span the entire 42 meter width of the three aisled nave, just 2 meters less than that of the Roman Pantheon, the largest dome in the world. And because the distance between the angles of the octagon were even farther apart at 45.5 meters, the average span of the dome would be marginally wider than that of the Pantheon. At 144 braccia, the height of the dome would evoke the holy number of the Heavenly Jerusalem mentioned in the Book of Revelation. By 1413, with the exception of one of the three apses, the east end of the church had been completed up to the windowed octagonal drum but the problem of building the huge dome did not yet have a solution. In 1417, the master builder in charge of the project retired and a competition for dome designs was begun in August 1418.