San Zaccaria is a church a short walk from Piazza San Marco that most visitors walk past without entering, which means most visitors miss one of the finest Renaissance altarpieces in Venice. Giovanni Bellini's Madonna Enthroned with Saints (1505), on the left wall of the nave, is considered one of his greatest works — a large, luminous, serene painting that rewards prolonged looking.
The church itself is an interesting hybrid: the lower parts of the facade are Gothic, the upper parts Renaissance, reflecting the decades it took to build in the late 15th century. The crypt, with its flooded foundations, contains the bones of eight doges of Venice. It is a matter of a few minutes' detour from the main tourist circuit and usually quiet enough that you can stand in front of the Bellini for as long as you like.