People say the canals make Amsterdam the Venice of the North - without the pigeons and the Italians, of course. The big four are the Prinsengracht, Herengracht, Keizersgracht and Singel. The main canals bisecting these four are the Brouwersgracht, the Bloemgracht, the Leliegracht, Leidsegracht and the Reguliersgracht. Others were filled in. If you see the word gracht on a street name, it was once water.
The 17th century canal belt has now been included on the Unesco list of world heritage sites. Opponents fear this will turn the centre into even more of a living museum than it is now.
For all the tourist clichés, a canal boat tour is a really good way to see the city, if you can ignore the prerecorded commentary which will blast out in German even if there are no Germans on board. You can pick up a boat trip all over the city centre. They all follow much the same route.