Its cathedrals, tall buildings and clean, narrow streets, it's wall drawings, huge groups of tourists and small water streams under trees and streetlamps are just lovely.
The cities in the Netherlands are very well organized and even an easily-get-lost person like myself can get around. Plus they have delicious food and crunchy ice cream which help with the whole orientation process.
Here's a few pics from Maastricht, the city devided in two by the river Maas:
