The tower of San Cristoforo, also known as Mariano II or Porta Manna, is located in Oristano and it was originally one of the gateways to the city. An inscription once inserted into the tower and today preserved in the Artificial Antiquarium, proves that it was built in 1290. It is today one of the few surviving elements of the city wall built by the Arborean judge Mariano II. The denomination of the tower of San Cristoforo is due to the retablo of San Cristoforo, a time guarded in the structure