AquaDom & Sea Life Berlin is hardly the greatest aquarium in Europe, but it has some unique features. The tanks begin on the River Spree and then flow into the Wannsee, a Berlin lake, before heading to the ocean. Thus, you go from freshwater to saltwater. Along the way you meet some 4,000 marine creatures from the octopus to the hound shark, even sea horses. After a Sea Life visit, you can go to the AquaDom to view the largest free-standing aquarium in the world. It’s home to a vast collection of rainbow-hued tropical fish. At the end of your visit, you take a dramatic glass elevator through a silo-shaped “fish tank” to the exit.