Here's an odd little collection of well-heads (vere da pozzo) with walls built through them, splitting them in half. Not sure why this happened since I think they are movable; maybe they were too heavy or it was too inconvenient to move them out of the way? And is the other half visible on the other side of the wall?
This first one, in Dorsoduro, is made of pink marble from Verona. I found this one when doing part of a walking tour from J.G. Links' "Venice for Pleasure." Mr. Links recommends a "curious little digression" off the beaten path to see a house not far from Campo Santa Margherita:
"Someone has built his garden wall through a well-head. The house belonging to the garden, which is numbered 3368, is...one of the oldest in the city, old even for Venice."
This one is in a courtyard in Castello~
Here's another one in a gated corte in Santa Croce~
And this is my favorite, inside a charming corte in Dorsoduro. This one just looks so droopy!