Ravenna

Ravenna is the capital of its province in Emilia-Romagna, and was the capital of the Western Roman Empire through the fifth century until the empire’s collapse in 476, after which it served as capital of the Ostrogothic Kingdom and then of the Byzantine Exarchate of Ravenna. That sequence is why it holds the finest late-antique mosaics in the world, in a handful of small brick buildings that give no hint from outside of the gold inside them. The historic centre is flat and walkable.