Like many hotels in Italy, Hotel Mercurio is located in a very old building. It is located on the 2nd and 3rd floors. There is no elevator to get to the second floor. The room and bathroom were very clean. Bed was one of the better ones we had during our time in Italy. Nice size of room, with a window overlooking a small courtyard. Hotel staff was friendly.
Central location, five minutes from St. Mark's Square.
Nice place, but not as typically traditional Venetian style as some others. (for instance, no green or red flocked fabric wall designs).
As far as convenience, it was very convenient, in the middle of San Marco district.
I would recommend it.
The coolest thing about this hotel is that it is right off the Canal of Barcaroli and the gondoliers serenade at night and in the morning. Ask for a room off the canal because it's worth it for atmosphere.
Also, the house that Amadeus Mozart lived in while he was in Venice was directly across from the hotel room window.