Having played a critical but sometimes forgotten role in history, Ravenna was the capital of the Western Roman Empire when it fell in 476. Then beginning a few decades later, it became the Italian capital of the Byzantine Empire for two centuries. During these periods, the city’s many famous and gorgeous mosaics were created, including a staggering eight locations that have been designated UNESCO World Heritage Sites. The oldest, from about 430, is the Mausoleum of Galla Placidia.