The Old Fortress (Fortezza Vecchia) was built on an elder castle structure built by Pisa and Countess Matilda of Tuscany; in 11th century. The tower of this harbour castle; called Mastio di Matilde; was integrated in the later built harbour castle; built most probably by Antonio da Sangallo the Elder; from 1521 to 1534. In 1377; the Pisa buildings were unified as the so called Quadrattura dei Pisani. Building of the Fortezza Vecchia was started in 1519; and ended 1534 under the rule of Alessandro de`Medici. The castle has three bastions: Closest to the land is the Ampolletta Bastion (Bastione dell`Ampolletta) at the Dorsena Vecchia (Old Dock); the Canaviglia Bastion (Bastione della Canaviglia) nearest to the Medicean port and the Bastione della Capitana (Capitana Bastion) at the Northeaastern side of the fortress. After 1769; the fortress was also used as a prison for the last remaining slaves of the Livorno based bagno dei forzati; once also a big slave market with up to 2;000 prisoners and slaves.