dChan - Q Origins Project Archive

Persian kings used domed tents in their official audiences to symbolize their divinity, and this practice was adopted by Alexander the Great.

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 ("Golden House") also made the dome an essential feature of palace architecture.[9] 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.[10] 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."[11]

The semi-domed apse became a symbol of Roman imperial authority under Domitian and depictions of emperors into the Byzantine period used overhead domes or semidomes to identify them.[12] Karl Swoboda writes that even by the time of Diocletian, the dome probably symbolized sovereignty over the whole world.[13] Roman imperial reception halls or throne rooms were often domed with circular or octagonal plans and, according to Nicholas Temple, "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.[11] Michele Melaragno writes that the concept of "Christ the King" was the Christian counterpoint to the Roman tradition of emperor deification and so absorbed the dome symbolism associated with it.[14]

https://en.m.wikipedia.org/wiki/Symbolism_of_domes