Den Bla Planet

Den Bla Planet, the Blue Planet, is Denmark's National Aquarium and one of the largest in Europe, and its building is as memorable as anything inside. Designed by the Danish architects 3XN and opened in 2013, it sits on the shore at Kastrup, beside the airport, and from above its silver-clad wings spiral out like a whirlpool, an image that carries on inside, where the curved foyer leads out to the different worlds of water. The highlight is the Ocean Tank, a huge tank viewed through a great panoramic window and a tunnel, where sharks, rays and large shoals of fish glide past, a sight that holds children and adults alike. Other areas take you to the coral reefs of the tropics, the cold waters of the North Atlantic and the Faroe Islands, the lakes and rivers of the world, and a warm rainforest with free-flying birds, reptiles and a sloth. The aquarium is one of the few places in Europe to see sea otters, and all of its otters were rescued from the wild, either orphaned or injured, which makes their enclosure one of the most popular, especially at feeding time. Daily feedings and talks run through the day and are worth planning around. The building has a cafe and a restaurant, and the outdoor areas look onto the Oresund. Den Bla Planet is open every day of the year, from 10:00 to 17:00 on most days, with longer evening hours on Mondays and every day in the peak seasons. Tickets are cheaper online than at the door, and the aquarium recommends booking ahead; children under three go free. Unlike most big Copenhagen attractions, Den Bla Planet is not included in the Copenhagen Card, so budget for it separately. Getting there is simple: take metro line M2 towards the airport to Kastrup station and walk about six hundred metres to the shore, or drive and use the paid car park. Allow two to three hours. It works especially well on a rainy day, on an arrival or departure day, given how close it is to the airport, or as a family outing combined with the beach at Amager Strandpark.

The architecture rewards attention. The whirlpool form was meant to evoke water drawn into the building, and the facade of small diamond-shaped aluminium shingles shifts in colour with the light and the sea. Inside, the visit is organised as a series of routes leading off the central foyer, so you can choose the areas that interest you and return to the centre between them, rather than following a single long path. This also makes it easy to take a break or to return to the Ocean Tank, which many visitors do more than once.

How to visit well: book tickets online for the lower price and to avoid the ticket queue, and check the day's feeding times when you arrive. Visit the sea otters at feeding time and the Ocean Tank at the start or end of the visit, when it is less crowded. Weekday mornings are calmer than weekends, and the aquarium is busy during Danish school holidays. The aquarium suggests bringing a stroller for babies, as it can be hard to carry small children through a long visit. The adults-only Blue Evenings, held on selected dates, are a different way to see the aquarium, with a calmer atmosphere.

Den Bla Planet fits neatly into a day in Amager, the island that holds the airport. Amager Strandpark, a long artificial beach with a lagoon and a promenade, is a short ride away and makes a pleasant walk in any season. The metro takes about a quarter of an hour back to Kongens Nytorv and the centre. For families planning several big days out, it pairs well with Copenhagen Zoo and Experimentarium, each worth its own day, and its position next to the airport makes it a good way to fill the hours before an evening flight.