Tamás snapped a few shots of some gondolas that moor along the wall.
As the sign on the wall says, that walkway is known as the "Fondamenta de la Preson". My guess is that it has something to do with those iron bars behind the guys in this next photo.
There are countless little places in Venezia where gondoliers tuck their boats in and run their cruises out of - some are more visible than others. This guy seems to have a more noticeable spot.
Martina Zane took some photos from almost exactly the same spot not long ago, some of them can be seen in my post "Ambulance Aftermath".
I'm sure that it's crazy at times, running a servizio out of that location, but it must be terrific to have the Rialto so close and be able to row under it whenever you want.