A dome is a structural element of architecture that resembles the hollow upper half of a sphere. Dome structures made of various materials have a long architectural lineage extending into prehistory.

Corbel domes have been found in the ancient Middle East in modest buildings and tombs. The construction of technically advanced large-scale true domes began in the Roman Architectural Revolution, when they were frequently used by the Romans to shape large interior spaces of temples and public buildings, such as the Pantheon. This tradition continued unabated after the adoption of Christianity in the Byzantine religious and secular architecture, culminating in the revolutionary pendentive dome of the 6th century church Hagia Sophia. With the Muslim conquest of the Sassanid Empire and the Byzantine Near East, the dome also became a feature of Muslim architecture (see gonbad, gongbei).

Domes in Western Europe became popular again during the Renaissance period, reaching a zenith in popularity during the early 18th century Baroque period. Reminiscent of the Roman senate, during the 19th century they became a feature of grand civic architecture. As a domestic feature the dome is less common, tending only to be a feature of the grandest houses and palaces during the Baroque period.

Many domes, particularly those from the Renaissance and Baroque periods of architecture, are crowned by a lantern or cupola, a Medieval innovation which not only serves to admit light and vent air, but gives an extra dimension to the decorated interior of the dome.

Characteristics

A dome can be thought of as an arch which has been rotated around its central vertical axis. Thus domes, like arches, have a great deal of structural strength when properly built and can span large open spaces without interior supports. Corbel domes achieve their shape by extending each circular layer of stones inward slightly farther than the previous, lower, one until they meet at the top. These are sometimes called 'false' domes. 'True', or 'real' domes are formed with increasingly inward-angled layers which have ultimately turned 90 degrees from the base of the dome to the top. Domes have been constructed from a variety of building materials over the centuries: from mud to stone, wood, brick, concrete, metal, glass and plastic.

History

Early history and primitive domes

There are numerous sporadic examples of cultures from pre-history to modern times constructing domed dwellings using local materials. Although it is not known when the first dome was created, the earliest known domed structures may be small dwellings made of Mammoth tusks and bones, dated from 15,000 to 20,000 years ago. Four of these were found by a farmer in Mezhirich, Ukraine in 1965 while he was digging in his cellar.

An Assyrian bas-relief from Nimrud depicts domed buildings, although remains of such a structure in that ancient city have yet to be identified due to the impermanent nature of sun-dried mudbrick construction.



Examples of mud-brick buildings which seemed to employ the "true" dome technique have been excavated at Tell Arpachiyah, a Mesopotamian site of the Halaf (ca. 6100 to 5400 BCE) and Ubaid (ca. 5300 to 4000 BCE) cultures. However, small corbel domes functioning as dwellings for poorer people appear to have remained the norm throughout the ancient Near East until the introduction of the monumental dome in the Roman period.

Buildings and tombs have been found from Oman to Portugal with a type of dome using the corbel technique. The similarities between the structures in Oman and those in Europe may be coincidental, however. The Oman structures, built above ground, date to around 3,000 BCE. The larger Treasury of Atreus, a Mycenaean tomb covered with a mound of earth, dates to around 1250 BCE.

The Wigwam was made by Native Americans using arched branches or poles covered with grass or hides. The Efe Pygmies of central Africa construct similar structures, using mango leaves as shingles. Another example is the Igloo, a shelter built from blocks of compact snow and used by the Inuit people, among others.

Roman and Byzantine domes

The Romans created domes using wood, stone, brick, ceramic, and concrete. The most famous Roman dome, and the largest, is in the Pantheon, a building in Rome originally built as a temple. Dating from the 2nd century, it is an unreinforced concrete dome resting on a thick circular wall, or rotunda. The circular opening at the top of the dome is called the Oculus, and it provides light and ventilation for the interior. The height to the oculus and the diameter of the interior circle are the same, 43.3 meters (142 ft). It remained the largest dome in the world for more than a millennium.

The Romans also used semi-domes, half a dome "cut" vertically, in niche and the exedra of secular (and later church) basilicas. By Late Antiquity, the exedra developed into the apse, with separate developments in Romanesque and Byzantine practice.

The first Roman dome in domestic architecture may have been in the palatial and opulent Domus Aurea, or "Golden House", of Nero (54-68 AD). A wooden dome is reported in contemporary sources to have covered the dining hall in the palace, and been fitted such that perfume might spray from the ceiling. The expensive and lavish decoration of the palace caused such scandal that it was demolished soon after Nero's death to make way for public buildings such as the Baths of Titus and the Colosseum.

"Within the [pagan] Roman world, domed constructions are limited almost without exception to the three environments of thermae, villas and palaces, and tombs. The Pantheon, as part of the Thermae of Agrippa, was no exception, whatever its religious character may have been." With the rise of Christianity and the end of the Western Roman Empire, domes became a signature feature of the religious and secular architecture of the surviving Eastern Roman Empire, often being built at the square intersections of perpendicular aisles.



To support those portions of a dome which would not rest directly on a square base, techniques were employed in the corners. Initially, corbelling in the corners or the use of arches called squinchs was used. The invention of pendentives, triangular segments of an even larger dome filling the spaces between the circular bottom of the dome and each of the four corners of the square base, superseded the squinch technique. The most famous Byzantine landmark, the church of Hagia Sophia, was their debut. Pendentives would become commonly used in Byzantine, Renaissance and baroque churches.

In the simple dome the pendentives are part of the same sphere as the dome itself, however such domes are rare.Sir Banister Fletcher, A History of Architecture. 18^th ed. London, Athelone Press(1975) ISBN 0-485550-01-6 In the more common compound dome, such as the Hagia Sophia, the pendentives are part of the surface of a larger sphere than the dome itself but whose center is at a point lower than that of the dome.

When the Hagia Sophia was completed in 537, it was the largest church in the world, and remained so for nearly a thousand years, until the completion of the Seville Cathedral in 1520. Its large central dome was 31.24 meters (102 ft 6 in) wide and 55.6 meters (182 ft 5 in) above the floor, about one fourth smaller and greater, respectively, than the dome of the Pantheon. Unlike the Pantheon, the peak of the dome was solid, and the base was pierced with a ring of windows. Additionally, two huge half-domes of similar proportion were placed on opposite sides of the central dome.

With the decline in the empire's resources following crisis and territorial losses, domes in Byzantine architecture were used as part of more modest buildings. The Cross-in-square plan, with a dome at the crossing, became most popular in the middle and late Byzantine periods. Resting the dome on a circular wall pierced with windows called a drum, or tholobate, eventually became the standard style. The combination of pendentive, drum, and dome was continued in the buildings of the Italian Renaissance.

Middle Eastern and Western European domes

Ruins of the Palace of Ardashir, dating from 224, demonstrate the use of the dome in the Sassanid Empire in what is today Iran. Sassanid architecture likely inherited an architectural tradition of dome-building dating back to the earliest Mesopotamian domes.



The Ostrogothic king Theodoric the Great built the Mausoleum of Theodoric in Ravenna, Italy, in 520, 44 years after the end of the Western Roman Empire. The 10 meter wide dome over the mausoleum was carved out of a single 300 ton slab of stone, very unusual at a time when most domes were made with bricks.

The Dome of the Rock in Jerusalem, the earliest existing Islamic building, dates to between 685 and 691. It was reportedly inspired by the domes of nearby Byzantine churches, such as the nearby Church of the Holy Sepulchre, and resembles the design of a Byzantine martyrium. The dome, made of wood, is approximately 20 meters in diameter and covered with gold.



Charlemagne, the Holy Roman Emperor, built the Palatine Chapel in his palace at Aachen in the 790s. The chapel's construction was heavily influenced by the Byzantine Basilica of San Vitale in Ravenna. The octagonal dome was the largest dome north of the Alps at that time.

St Mark's Basilica in Venice, Italy, has changed and developed over hundreds of years. The current church was built by 1063, replicating the earlier Greek cross plan with five domes (one each over the four arms of the cross and one in the center). These domes were built in the Byzantine style, perhaps 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. So impressive were the gilded mosaics covering the interior that from the 11th century on the building was known by the nickname Chiesa d'Oro (Church of gold). Much higher wooden, lead-covered, outer domes with cupolas were added sometime during the first half of the 13th century.

Italian Renaissance and Ottoman domes

Brunelleschi's octagonal brick dome for the Florence Cathedral was built between 1420 and 1436. Santa Maria del Fiore, also known as the duomo of Florence, measures 42 to 45 meters in diameter, depending on whether the base of the dome is measured from face to face, or angle to angle. Eight white stone external ribs mark the edges of the eight sides, next to the red tile roofing, and extend from the base of the dome to the base of the cupola. It was the largest dome built in Western Europe since the Pantheon, and remains the largest masonry dome ever built. Notably, it was built as a double dome, with inner and outer shells, a technique that would become more and more common.



Süleymaniye Mosque, built in Constantinople (modern Istanbul) from 1550 to 1557, has a main dome 53 meters high with a diameter of 26.5 meters. At the time it was built, the dome was the highest in the Ottoman Empire when measured from sea level, but lower from the floor of the building and smaller in diameter than that of the nearby Hagia Sophia.

The Selimiye Mosque in the city of Edirne, Turkey, was the first structure built by the Ottomans which had a larger dome than that of the Hagia Sophia. The dome sits on an octagonal base and has an internal diameter of 31.25 meters. Designed and built by architect Mimar Sinan between 1568 and 1574, when he finished it he was 86 years old, and he considered the mosque to be his masterpiece.

The double walled dome of St. Peter's Basilica was completed in 1590. Slightly smaller in diameter than those of the Pantheon and Florence Cathedral, the inner dome is hemispherical, while the outer ribbed dome is vertically oval. The outside of the drum is decorated with pairs of columns between the large windows. Its internal diameter is 41.47 meters (136.1 ft) and its external height from the ground to the top of the cross is 136.57 meters (448.1 ft). The dome remains the tallest in the world. The style of the church ushered in what would become known as Baroque architecture, and the dome in particular would have great influence on subsequent designs.

Early modern period domes

The famous Saint Basil's Cathedral in Moscow, Russia, was built from 1555 to 1561. It's distinctive onion domes, created later in 1680s, are outstanding examples in Russian architecture.



Considered the finest example of Mughal architecture, the Taj Mahal is a mausoleum which combines elements of Persian, Indian, and Islamic architecture. It was built between 1632 and 1653. Its large marble dome, often called an onion dome or amrud (guava dome), is about 35 meters high and sits on a cylindrical drum about 7 meters high.



St. Paul's Cathedral in London was rebuilt from 1677 to 1708. When finished, the dome designed by Sir Christopher Wren was three layers: an inner dome with an oculus, a decorative outer wood dome covered in lead roofing, and a structural brick cone in between. The brick cone ends in a small dome, which supports the cupola and outer roof and the decorated underside of which can be seen through the inner dome's oculus. It rises 365 feet (108 m) to the cross at its summit. Evocative of the much smaller Tempietto by Bramante, it in turn inspired many of its own imitators, most famously the second US Capitol dome in Washington, DC.

Adjacent to a hospital and retirement home for injured war veterans, the royal chapel of Les Invalides in Paris, France, was begun in 1679 and completed in 1708. The dome was one of many inspired by that of St. Peter's Basilica and it is an outstanding example of French Baroque architecture. In 1861 the body of Napoleon Bonaparte was moved from St. Helena to the most prominent location under the dome.

Modern period domes

The dome over the United States Capitol building was built from 1855 to 1866. Although painted white and crowning a masonry building, the dome is actually cast iron, as are the internal support framework and stairs. The design was heavily influenced by the dome of St. Paul's Cathedral in London, among others.

In the 20th century, thin "eggshell" domes of pre-stressed concrete by architect-engineers such as Nervi opened new directions in fluid vaulted spaces enclosed beneath freeform domed space which now might be supported merely at points rather than in the traditional constricting ring. Geodesic domes were invented after World War I and popularized by Buckminster Fuller.

Many sports stadiums are domed, especially in climates that have widely-variable summer and winter weather. The first such stadium was the Astrodome in Houston, Texas. A major improvement to the domed stadium was accomplished with the construction of SkyDome, now Rogers Centre, in Toronto, Ontario, the first domed stadium with a retractable roof.

General types

Corbel dome

A corbel dome is different from a 'true dome' in that it consists of purely horizontal layers. As the layers get higher, each is slightly cantilevered, or corbeled, toward the center until meeting at the top. A famous example is the Mycenaean Treasury of Atreus.

Sail dome

A sail dome, more commonly called a sail vault, can be thought of as pendentives which, rather than merely touching each other to form a circular base for a drum or compound dome, smoothly continue their curvature to form the dome itself. The dome gives the impression of a square sail pinned down at each corner and billowing upward.

Saucer dome

A saucer dome is the architectural term used for a low pitched shallow dome which is described geometrically as having a circular base and a segmental (less than a semicircle) section. A section across the longer axis results in a low dome, capping the volume. A very low dome is a saucer dome. Many of the largest existing domes are of this shape.

Gaining in popularity from the 18th century onwards, the saucer dome is often a feature of interior design. When viewed from below it resembles the shallow concave shape of a saucer. The dome itself, being often contained in the space between ceiling and attic, may be invisible externally. These domes are usually decorated internally by ornate plaster-work, occasionally they are frescoed.

They are seen occasionally externally in Byzantine churches and Ottoman mosques. Most of the mosques in India, Pakistan, Iran and Afghanistan have these type of domes.

Onion dome

The onion dome is a bulbous shape tapering smoothly to a point, strongly resembling an onion, after which they are named, and exemplified by Saint Basil's Cathedral in Moscow and the Taj Mahal. They are found mostly in eastern architecture, particularly in Russia, Turkey, India, and the Middle East. An onion dome is a type of architectural dome usually associated with Russian Orthodox churches. Such a dome is larger in diameter than the drum it is set upon and its height usually exceeds its width.

Oval dome

The oval dome is closely associated with the Baroque style. The term comes from the Latin ovum, meaning "egg". Though the oval dome is typically identified with churches of Bernini and Borromini, the first baroque oval dome was erected by Vignola for a chapel, Sant'Andrea in Via Flaminia often called Sant'Andrea del Vignola. Julius III commissioned the dome in 1552 and construction finished the following year. The largest oval dome was built in the basilica of Vicoforte by Francesco Gallo.

Parabolic dome

A parabolic dome is a unique structure, in which bending stress due to the udl of its dead load is zero. Hence it was widely used in buildings in ancient times, before the advent of composite structures. However if a point load is applied on the apex of a parabolic dome, the bending stress becomes infinite. Hence it is found in most ancient structures, the apex of the dome is stiffened or the shape modified to avoid the infinite stress.

Polygonal dome

Technically domical vaults, these are domes which maintain a polygonal shape in their horizontal cross section. The most famous example is the Renaissance octagonal dome of Filippo Brunelleschi over the Florence Cathedral. Thomas Jefferson, the third president of the United States, installed an octagonal dome above the West front of his plantation house, Monticello.

Umbrella dome

Also called pumpkin, melon, scalloped, or parachute domes, these are a type of dome segmented by ribs radiating from the center of the dome to the base. The material between the ribs arches from one to the other, transferring the downward force to them. The central dome of the Hagia Sophia uses this method, allowing a ring of windows to be placed between the ribs at the base of the dome. The central dome of St. Peter's Basilica also uses this method.

Influential domes

Domes that have been disproportionately influential in later architecture are those of the Pantheon in Rome, Hagia Sophia in Constantinople (modern Istanbul), and the Dome of the Rock in Jerusalem. In Western architecture, the most influential domes built after the early Renaissance exploit of Brunelleschi's Florentine dome have been those of St. Peter's Basilica in Rome and Jules Hardouin-Mansart's dome at Les Invalides in Paris. The dome of St. Paul's Cathedral in London was the inspiration for the United States Capitol in Washington, which in turn inspired domes of most of the US state capitols.

Domes in buildings of worship

Domes also play a very important part in places of worship where they can represent and symbolise different aspects of the religion. Eastern orthodox churches, for example, have domes which represent heaven. The dome's purpose is to remind people that to gain God's blessing it is necessary to accept salvation through Christ.Domes can also be found in Islamic places of worship, called mosques. In an orthodox church the domes have pictures of Jesus whereas in Islam it is forbidden to show pictures of Mohammed during worship. Instead, mosques have decorations and patterns on the domes. The domes are tradition in Islam, and another reason for domes is so that the building can be distinguished and others can see where it is even from far.

See also

• Vault
• Geodesic dome
• Monolithic dome
• List of celebrated domes
• List of world's largest domes

References

Gallery

Image:Selimiye Camii.jpg|The exterior of the dome of Selimiye Mosque in Edirne.

Image:Pendentive and Dome.png|A compound dome (red) with pendentives (yellow) from a sphere of greater radius than the dome.

Image:Image-LittleHagiaSophiaInIstanbulDome.JPG|Dome of the former Church of Saints Sergius and Bacchus(today mosque of Little Hagia Sophia) in Istanbul.

Image:SFCityHallDomeInterior.JPG|Interior of the dome, San Francisco City Hall.

Image:Imam reza holy shrine.jpg|The dome of Imam Reza holy shrine, covered with gold-coated bricks, (built:1333 AD), Mashhad, Iran.

Image:St Joseph the Betrothed 080202.jpg| Interior of St. Joseph the Betrothed Ukrainian Greek Catholic Church in Chicago, Illinois depicting Christ Pantocrator as in traditional byzantine church style.

Image:Cupula Bellas Artes.jpg|Bellas Artes Palace, Mexico City.

Image:Kbh Marmorkirche 1.jpg|The Marble Church, Copenhagen.

Image:Dom Florenz Kuppelfresko.jpg|The interior dome of the Santa Maria del Fiore in Florence designed by Brunelleschi it was completed in 1436.