I’ve posted a number of images of capitelli, the small wall mounted shrines that seem to be an essential element of every street and square, and the logic of mounting small religious works above the flow of humanity is sound. In such narrow and busy streets any obstruction is unwelcome, but get away from the focal points in San Marco and San Polo and that is no longer such an important consideration.
Shrines like this are more common on the smaller islands in the lagoon, but I happened upon this version in the Castello area when scouting around the apartments near Rio Tera Garibaldi, the former canal that resembles an ordinary street. In what seemed like a back alley it seemed a strange location for an article of veneration, and the intricate gate was a barrier to experiencing the interior. Or am I missing the point?