Tucked away on a little calle in Castello north of Via Garibaldi, this lovely 14th century Gothic relief shows the Virgin and Child with saints Peter and Paul. The child is handing a key to Peter and a scroll to Paul.
The relief is over an entrance to a former religious complex that once included a hospice(Ospizio dei Santi Pietro e Paolo) for pilgrims on their way to the Holy Land, a convent, and an oratory dedicated to San Gioachino, father of the Virgin Mary. The hospice was founded in the 11th c. and was later converted to a hospital which was one of the largest in Venice. The complex was closed by the French in the early 19th century; now it's city property and I've never found it open and don't know what (if anything) it's used for today.