The origins of this city date back to ancient times. It was an important Etruscan and Roman centre, and the seat of the Christian Diocese in the fourth century. The Lombards occupied Arezzo at the end of the sixth century AC, and had a great influence on the city during this time. In the Middle Ages, Arezzo became a powerful free city, often guided by its bishops, who were Counts of the Holy Roman Empire. The city was at war with Siena, but primarily with Florence, who subjugated it in 1384. From this date on, with the exception of two rebellions, one in 1502 and one from 1529-1530, its history is merged with that of the dominating city as well as with that of Tuscany. The current historical centre of the town still holds all the fascination of an illustrious past and its main monuments are enriched by the works of great medieval and Renaissance artists such as Cimabue, Piero della Francesca, Andrea della Robbia and Giorgio Vasari.