Claim: By the time of Diocletian, a Roman emperor, the domes had already gained their symbolism of superiority.
Evidence: Diocletian (/ˌdaɪ.əˈkliːʃən/; Latin: Gaius Aurelius Valerius Diocletianus; born Diocles; 22 December c. 244 – 3 December 311) was a Roman emperor from 284 to 305. Imperial mausolea, such as the Mausoleum of Diocletian, were domed beginning in the 3rd century. Karl Swoboda writes that even by the time of Diocletian, the dome probably symbolized sovereignty over the whole world.