Venezia (Venice) is without doubt one of the most fascinating cities in Europe and a must see activity in it's entirety -though don't go in summer! As you won't see anything for people; it was bad enough when I went in April.
It was from here that Marco Polo set sail for China and it is just packed with historical sites. The town itself really is an open air museum.
Remember it's sinking so get in there while you can! Venezia is built on 117 small islands and has about 150 canals. The city is divided into 6 sections (sestieri) which are :Canaregio, Castello, San Marco, Dorsoduro, San Polo and Santa Croce. Beware because there is no logic to the street numbers so you can get lost easily; as I did upon arrival in the middle of the night looking for our hostel!
There are no cars in the city, you either have to walk, get a train or take to the canals. However, the water Taxi's are VERY expensive and the Vaporettos are expensive too (as are Gondolas).