Florence was established by Lucius Cornelius Sulla in 80 BC as a settlement for his veteran soldiers and was named originally Fluentia, owing the fact that it was built between two rivers, which was later corrupted to Florentia. It was built in the style of an army camp with the main streets, the cardo and the decumanus, intersecting at the present Piazza della Repubblica. Situated at the Via Cassia, the main route between Rome and the north, and within the fertile valley of the Arno, the settlement quickly became an important commercial centre. The Emperor Diocletian is said to have made Florentia the seat of a bishopric around the beginning of the 4th century AD, but this seems impossible in that Diocletian was a notable persecutor of Christians.
In the ensuing two centuries, the city experienced turbulent periods of Ostrogothic rule, during which the city was often troubled by warfare between the Ostrogoths and the Byzantines, which may have caused the population to fall to as few as 1,000 people. Peace returned under Lombard rule in the 6th century. Florence was conquered by Charlemagne in 774 and became part of the Duchy of Tuscany, with Lucca as capital. The population began to grow again and commerce prospered. In 854, Florence and Fiesole were united in one county