During the 6th century a castle stood on San Pietro island which is how the Castello Sestiere district got its name. In 774 it was called Olivolo Island because the first episcopal see of Venice was founded here. It remained the center of the Roman Catholic archdiocese until 1451 when that designation moved to St. Mark’s Basilica. This brick, castle-like wall with the bell tower and moored boats is a few steps away from the island’s Basilica di San Pietro.
