Basilica di San Marco
It is the most famous of the city's churches and one of the best known examples of Byzantine architecture. It lies at the eastern end of the Piazza San Marco, adjacent and connected to the Doge's Palace. Originally it was the chapel of the Doge, and has only been the city's cathedral since 1807, when it became the seat of the Patriarch of Venice, archbishop of the Roman Catholic Archdiocese of Venice, formerly at San Pietro di Castello.
For its opulent design, gilded Byzantine mosaics, and its status as a symbol of Venetian wealth and power, from the 11th century on the building has been known by the nickname Chiesa d'Oro (Church of gold). - Wikipedia