The Byzantine era is usually dated from 330 AD, when Constantine the Great moved the Roman capital to Byzantium, which became Constantinople, until the fall of the Byzantine Empire in 1453. However, there was initially no hard line between the Byzantine and Roman empires, and early Byzantine architecture is stylistically and structurally indistinguishable from earlier Roman architecture. This terminology was introduced by modern historians to designate the medieval Roman Empire as it evolved as a distinct artistic and cultural entity centered on the new capital of Constantinople (modern-day Istanbul) rather than the city of Rome and its environs.