The small octagonal fort on the central square is the town's founding monument and the origin of its name. Built in 1788 on the orders of Grand Duke Pietro Leopoldo of Tuscany, it was designed to protect the marble stockpiles on the beach from coastal raids — at the time, freshly quarried blocks from Carrara were dragged down to this point on wooden sledges and loaded onto barges. The fort has been repurposed many times over the centuries (barracks, prison, warehouse) and now houses a small museum dedicated to the town's marble-trading history. The square around it — Piazza Garibaldi — is the social centre of the town and the starting point of the evening passeggiata.