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.
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. 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. The Scythians built such domed tombs, as did some Germanic tribes in a paraboloid shape. By Hellenistic and Roman times, the domical tholos had become the customary cemetery symbol. Lukas Nickel writes 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 writes 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 writes 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. Rudolf Wittkower writes that a "cosmic interpretation of the dome remained common well into the eighteenth century."
Divine ruler
Herbert Howe writes 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. 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.
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. Persian kings used domed tents in their official audiences to symbolize their divinity, and this practice was adopted by Alexander the Great. 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. One way the Romans depicted the celestial tent in architecture was as a corrugated or gored dome.