The tower of San Cristoforo or Porta Ponti, also known as Torre di Mariano II, stands alone in the center of Piazza Roma, and truly evokes the noble past of medieval Oristano. The tower includes various wooden structures and apparatuses. A winch positioned on the second floor operates a small drawbridge through chains and ropes, the loops of which are still visible at the rear of the tower. A roller shutter and a high double-leaf door complete its safety system.