It is dominated by an old prison built by the Bourbons, completed in 1797 and in use until 1965. It has 99 cells around a central watchtower. Built for 600 inmates, it had 800 in 1817 (and 400 on Ventotene). People imprisoned included Carmine Crocco, the most important brigand during the Italian unification, and the anarchist Gaetano Bresci, who killed King Umberto I in 1900. He was imprisoned there for a year before being found hanged in his cell. During the Fascist regime, other prisoners were the future President of Italy Sandro Pertini, Umberto Terracini, Giorgio Amendola, Lelio Basso, Mauro Scoccimarro, Giuseppe Romita, Altiero Spinelli and Ernesto Rossi.