A vera da pozzo is a well or well-head, and there are so many of these things all over Venice that it’s easy to stop noticing them after a while. They aren’t true wells, they're cisterns that were used for collecting and filtering rainwater and until the mid-1800’s, they were the only source of fresh water in the city. During times of drought, the Republic would haul water in by barge and fill these up. After Venice was connected to an aqueduct on the mainland, many of these were removed and the remaining ones covered over, but there are still a bunch of them around and many of them are very beautiful.
In “Strolling through Venice,” John Freely writes that there used to be 6,782 of these wells; today, there are hundreds still to be seen in public places. He identifies and dates many of them in the walking tours in his book. Some of them are decorated with carvings and reliefs, and I try to remember to look at the ones close to churches because they usually have some art connected to the church’s name saint.
According to Freely, this one used to be a baptismal font in a church.
This very worn but sweet relief shows Tobias and the Angel (Archangel Raphael) and is on a well by the church of Angelo Raffaele in Dorsoduro.
This relief of Archangel Gabriel carrying the annunciation lily is on the vera da pozzo in Campo Sant’ Angelo in sestiere San Marco.
This relief shows Saint George and the Dragon; it’s on the well next to the church of San Giorgio dei Greci in Castello.
A 19th century photo by Carlo Naya showing folks getting water from one of the bronze wells in the courtyard of the Palazzo Ducale.
Update: here's a link to Anne's wonderful post about "The Lady of the Well" that we were discussing in the comments below.