Denmark's Aquarium, Den Blå Planet, opened in 2013 with a fantastic location right next to Øresund and equally fantastic architecture. It's about a 600 meter walk from Kastrup Metro Station to the aquarium, and if you follow the blue wave benches, you'll be led directly into the large aquarium, which houses thousands of animals from all over the world frolicking in the aquarium's seven million liters of azure blue saltwater.
In addition to puffins and hammerhead sharks, Kastrup Station is also close to the Kastrup Farm Art Museum, an old country house now furnished as a museum with modern graphics and contemporary art.