We stayed in the separate Wellness Suite, the building is 1-2 min away from the main hotel and the entrance could look a bit sketchy (as if you would walk in any other house on the street, only a doorbell indicates the room), but the comfort offered by the room in unbelievable. You have a sauna, huge shower that is also a steam room, jacuzzi and separate living room. It could easily be a fully equipped apartment. Location is extremely convenient and close to San Zaccaria ferry stop.
If you don't need breakfast in the morning, as walking to the main hotel might result annoying, you can just buy something and have a coffee or tea in the room with the complimentary machines.
Whenever you read that rooms in Venice are small, you haven't seen this wellness suite.