Built by the powerful priors, the Palace of Lords was started in 1299 and finished ten years later to plans by Arnolfo di Cambio (the architect of the first phase of the cathedral). Originally of Gothic inspiration and designed as a fortified structure (blind walls on the lower level, watch path, battlements and machicolation), it was later altered by Vasari who was commissioned by Cosimo I to turn it into a Renaissance palace and the venue for sumptuous festivities.