The church of San Pietro di Castello, located on the island of Olivolo, was the first religious centre in Venice. It was the cathedral until 1807, before the title was given to San Marco. Originally dedicated to Saint Sergius and Bacchus in the VIIth century, it was later dedicated to Saint Peter in the IXth century. Inside this latin cross shaped church topped by a dome is Saint Peter's throne coming from Antioch. According to the legend, within the throne was hidden the Saint Graal. It is made of a Muslim funeral stele decorated with arabic motifs and Qu'ran versets. The remains of Venice's first patriarch, San Lorenzo Giustiniani, lie there.