Once every three weeks I visit Artis, the ZOO in Amsterdam, together with my 2 year old son. He loves it, and knows all animals by name, and nickname (the mandril's name is Picasso ;-)
Although small, the Artis aquarium has some absolutely stunning setups. In the main hall they have several freshwater tanks, that I really like because of the way they used the tree roots, rocks and plants to create great depth. The use of HQI lights adds to the mystical feeling.
Some of my favourite tanks:
Another great tank is the massive Amazon underwater Forest, containing Arapaima's, arowana's, pacu's and red tail catfish:
They also keep an absolutely stunning couple of Cichlasoma citrinellum, or Midas cichlid:
If you're in an aquarist club, you can visit behind the scenes.