The eastern gate of the medieval walls, named for the clock set into its arch. It is the most photogenic of the three surviving gateways of the 14th-century Florentine fortification known as the Castello di San Michele Arcangelo al Ponte a Sieve.
Walking through it puts you on the old commercial street that ran the length of the fortified town toward the Medici bridge. The clock is still wound by hand. Pause to look at the brackets and the worn stone above the arch — five hundred years of carts and trucks have left a polished groove down the centre of the road.