Well, let me suggest you an idea of a truly unforgettable night in Venice (expirienced by myself). If you are lucky and your hotel is in Venice (or if you are not afraid of spending the whole night in a city where everything is closed until 6 AM), go to Piazza San Marco. Go there at 3-4 AM. You will be alone there. Pick up a chair from Gran Caffe Quadri (facing the Basilica San Marco, to the left, even in the winter they keep their chairs in the street), fix it right in the middle of the square (piazza) and sit on it. Face the basilica, it is one of the most brilliant buildings in the world. Just you and the Basilica. Nobody else. Silence. History. Very personal. Pigeons sleeping in their crowd 20 meters from you. Soon there will be a lot of people, but this time it`s a Venice of your own. Silence...
So, that`s my idea of a truly unforgettable night in Venezia (Venice).
P.S. And don`t forget to return the chair!