The symbolic meaning of the dome has developed over millennia. Although the precise origins are unknown, a mortuary tradition of domes existed across the ancient world, as well as a symbolic association with the sky. Both of these traditions may have a common root in the use of the domed hut, a shape which was associated with the heavens and translated into tombs.
The mortuary tradition has been expressed in domed mausolea, martyria, and baptisteries. The celestial symbolism was adopted by rulers in the Middle East to emphasize their divine legitimacy and was inherited by later civilizations down to the present day as a general symbol of governmental authority.
Origins The meaning of the dome has been extensively analyzed by architectural historians. According to Nicola Camerlenghi, it may not be possible to arrive at a single "fixed meaning and universal significance" for domes across all building types and locations throughout history, since the shape, function, and context for individual buildings were determined locally, even if inspired by distant predecessors, and meaning could change over time. Cyril Mango wrote that a symbolic interpretation of architecture was consistent with "the workings of the medieval mind", although simply accepting a celestial meaning of the dome and an imperial connotation for the ciborium, for example, did not explain the variety of forms. Yasser Tabbaa considered domes to be the "ultimate aesthetic statements of many architectural traditions and as repositories of iconography and cosmology".
Mortuary tradition According to E. Baldwin Smith, from the late Stone Age the dome-shaped tomb was used as a reproduction of the ancestral, god-given shelter made permanent as a venerated home of the dead and the instinctive desire to do this resulted in widespread domical mortuary traditions across the ancient world, from the stupas of India to the tholos tombs of Iberia. Michele Melaragno noted that the Scythians built such domed tombs, as did some Germanic tribes in a paraboloid shape.
Per Smith, by Hellenistic and Roman times, the domical tholos had become the customary cemetery symbol. Jodi Magness noted that domed ceilings in Jewish catacombs in Rome displayed images of the menorah by the 3rd or 4th century in order to evoke the Temple and because the number seven represented, in the words of Rachel Elior, the "span of time needed for the transition from chaos to Creation, from impurity to purity and from death to life."
Lukas Nickel wrote that the conception of a round heaven over a square earth may have contributed to the Han Chinese' rapid adoption in the first century AD of square base cloister vault chambers in their tomb architecture.
Celestial tradition Smith wrote that in the process of transforming the hut shape from its original pliable materials into more difficult stone construction, the dome had also become associated with celestial and cosmic significance, as evident from decoration such as stars and celestial chariots on the ceilings of domed tombs. This cosmological thinking was not limited to domed ceilings, being part of a symbolic association between any house, tomb, or sanctuary and the universe as a whole, but it popularized the use of the domical shape.
Michele Melaragno wrote that the nomadic tribes of central Asia are the origin of a symbolic tradition of round domed-tents being associated with the sky and heavens that eventually spread to the Middle East and the Mediterranean. Smith noted that one way the Romans depicted the celestial tent in architecture was as a corrugated or gored dome.
Theresa Grupico stated that domes and tent-canopies were also associated with the heavens in Ancient Persia and the Hellenistic-Roman world. A dome over a square base reflected the geometric symbolism of those shapes. The circle represented perfection, eternity, and the heavens. The square represented the earth. An octagon was intermediate between the two. Ancient peoples associated the circle with the cosmos, according to Jack Tresidder, due to the shapes of the sun and moon, because it is a form that has no beginning or end, because of the cyclical movements of the planets, and because of the cycle of the seasons. Circular domes incorporated this celestial symbolism.
Karl Lehmann stated that both pagan and Christian use of domes reflected a vision of the "physical as well as the transcendental celestial realm." A "cosmic interpretation of the dome remained common well into the eighteenth century," according to Rudolf Wittkower.
Divine ruler Herbert Howe wrote that throughout the Middle East domes were symbolic of "the tent of the ruler, and especially of the god who dwells in the tent of the heavens." Passages in the Old Testament and intertestamental literature document this, such as Psalms 123:1, Isaiah 40:22, I Kings 8:30, Isaiah 66:1, Psalms 19:4, and Job 22:14. Michele Melaragno wrote that Persian kings used domed tents in their official audiences to symbolize their divinity, and this practice was adopted by Alexander the Great. According to Michael Walter, a tradition of the "golden dome" identifying the ruler with the cosmos, sun, and astrological values originated in Persia and spread to later Roman and Turkic courts.
According to Smith, the distinct symbolism of the heavenly or cosmic tent stemming from the royal audience tents of Achaemenid and Indian rulers was adopted by Roman rulers in imitation of Alexander, becoming the imperial baldachin. This probably began with Nero, whose Domus Aurea, meaning "Golden House", also made the dome a feature of Roman palace architecture. According to Nicholas Temple, Nero's octagonal domed room in his Domus Aurea was an early example of an imperial reception hall, the symbolism of which "signaled an elevation of the status of the emperor as living deity, which in the case of Nero related specifically to his incarnation as Helios and the Persian Mithra." Melaragno wrote that the allegory of Alexander the Great's domical tent in Roman imperial architecture coincided with the "divinification" of Roman emperors and served as a symbol of this. The domical octagonal hall in the Flavian Domus Augustana is another example of the octagon's imperial symbolism in antiquity, which Temple says may have been related to hero ruler-ship, mediation between the terrestrial and celestial, or the divine harmony of the octave. Colum Hourihane wrote that the semi-domed apse became a symbol of Roman imperial authority under Domitian and depictions into the Byzantine period used overhead domes or semidomes to identify emperors.
The meaning of the Pantheon appears to have been uncertain even to the Romans within a century of its construction and remains a mystery. Christiane Joost-Gaugier suggested that the dome of the Pantheon represented the accord of the sun and the moon because of references to Pythagorean numerology, with the single oculus representing the sun, the 28 columns of coffers representing the moon due to the days in the lunar month, and the five rows of coffers representing marriage due to the inclusion in five of two and three (female and male). The dome was a hemisphere because the sphere was to the Pythagoreans the perfect form and represented the universe. Giangiacomo Martines wrote that the use of the number 28 in the dome represented perfection because it was considered a perfect number going back to the Pythagoreans and was "associated with virtue, moderation, and beauty". Edmund Thomas noted that the five rows of coffers correspond to the five planets recognized by the ancient Romans. He wrote that the dome was "dominated centrally by the intrusion of the real sun" and that the 28 sets of coffers corresponded to the phases of the moon. Robert Hannah and Giulio Magli proposed that light from the Pantheon's oculus would illuminate the entrance on the traditional anniversary of the founding of Rome and could have been used to symbolize the inclusion among the gods of an emperor standing there as part of a ceremony.
Edmund Thomas wrote that Roman arcuated lintels and domes were used as canopies for the statues of gods, but "cosmic imagery and ciborium forms" were linked to the worship of the emperor under Antoninus Pius, who issued a coin with a cusped dome that "associated the emperor with the light and power of the sun". Karl Swoboda wrote that even by the time of Diocletian, the dome probably symbolized sovereignty over the whole world. Nicholas Temple stated that Roman imperial reception halls or throne rooms were often domed with circular or octagonal plans and "functioned as a ceremonial space between the emperor, his court and the gods", becoming a common feature of imperial palaces from the time of Constantine onwards.
The domed throne room of Sassanid Persian king Khusrau, decorated with the image of the king alongside "heavenly luminaries (including the signs of the zodiac)", was given by Jodi Magness as an example of the cosmic dome decoration originating in the ancient Near East that "was designed as an earthly reflection of the heavenly hierarchy."
Christianity E. Baldwin Smith wrote that, by the Christian era, "cosmic imagery had come to transcend the mortuary, divine and royal symbolism already associated with the dome" but the Christian use of domes acknowledged earlier symbolic associations. Thomas Mathews wrote that Christianity's rejection of astrology was reflected in the omission of signs of the zodiac imagery from its dome decoration. According to Gillian MacKie, early Christian domes were often decorated at the base with imagery of the Four Evangelists, symbolizing "the idea that the microcosmic vision of heaven was supported by the word of God as revealed in the Gospels."
According to Susan Balderstone, domed centralized plans, whether octagonal, circular, or tetraconch, were "associated with the influence of Arianism in the fourth century and with the Monophysites in the fifth century." Robert Stalley wrote that mausolea, martyria, and baptisteries shared similar forms in the Roman architectural tradition as domed centralized plans due to representing the linked ideas of "death, burial, resurrection, and salvation".
Martyria Smith wrote that the dual sepulchral and heavenly symbolism was adopted by early Christians in both the use of domes in architecture and in the ciborium, a domical canopy like the baldachin used as a ritual covering for relics or the church altar. The traditional mortuary symbolism led the dome to be used in Christian central-type martyria in the Syrian area, the growing popularity of which spread the form. The spread and popularity of the cult of relics also transformed the domed central-type martyria into the domed churches of mainstream Christianity. According to Nicholas Temple, the use of centralized buildings for the burials of heroes was common by the time the Anastasis Rotunda was built in Jerusalem, but the use of centralized domed buildings to symbolize resurrection was a Christian innovation. Richard Krautheimer noted that the octagonal pattern of Roman mausolea corresponded to the Christian idea of the number eight symbolizing spiritual regeneration.
Baptisteries