Of course the Red Light Dictrict Area
You can find a penis fountain, the Hash Museum, triple Xs dildo/bollards along the line (thus, the XXX term came from), or Hash Brownies. Absinthe is legal, so don't miss out the opportunity to have a shot in the 'coffee shop'
Anne Frank Huis is interesting, along with the van Gogh Museum. If you care for a day excursion, you can go to
Zaanse Schans to see windmills along a river, or Volendam village: a fisherman village that died out when they constructed the North Dam, or even to the Zuiderzee/North Sea Dam.