3XN’s Blue Planet Aquarium: A Giant Whirlpool of Architecture

Aerial view of the National Aquarium of Denmark in Kastrup; photo Dragoer Luftfoto, courtesy of 3XN Architects.

The architecture of The Blue Planet – National Aquarium of Denmark by 3XN Architects

I’ll be frank: I enjoy aquariums, but I usually dislike their buildings. Most fall into one of two categories—uninspired metal boxes that resemble emergency shelters after a disaster, or glass‑and‑plasterboard concoctions so kitsch they would have been rejected even in Coney Island’s darkest days.
Exceptions are rare, and to find an outstanding exception is like stumbling upon the Koh-i-Noor while walking your dog.
The Blue Planet, Denmark’s National Aquarium in Kastrup, just south of central Copenhagen, is one of those rare anomalies—and perhaps the most impressive of them all.

Designed by Danish firm 3XN and completed in 2013, The Blue Planet brilliantly fuses theme and form. Its architecture embodies water and the life within it, translating the essence of the aquarium into built space.
The building’s defining gesture is its 97,000‑square‑foot aluminum‑clad whirlpool. This swirling form, both iconic and evocative, recalls the “shape of water” itself and nods to the legendary maelstroms described by Poe and Verne. It is not only symbolic but also functionally apt.

Each of the five spiraling arms houses a distinct program.
The first contains a long arrival ramp and entrance hall; the second, an auditorium, educational facilities, and a café. The remaining three arms host the permanent exhibitions: one dedicated to seas and oceans, another to rivers and lakes, and the third to Denmark’s cold waters. All five arms coil around a central foyer, allowing visitors to access each exhibition independently.

Photo Adam Mørk – courtesy of 3XN/AS

National Aquarium of Denmark by 3XN Architects: bird’s eye view, first floor, roof plan, and conceptual scheme. Courtesy of 3XN Architects.

To realize this complex geometry, 3XN collaborated with engineering firm Moe & Brødsgaard. Using advanced Building Information Modeling (BIM), they detailed the building’s curving steel structure—over 700 tons in total—and its flowing aluminum skin.

BIM model of the Blue Planet Aquarium building. Courtesy of 3XN Architects.

Cross-sections. Courtesy of 3XN Architects.

Photo Adam Mørk – courtesy of 3XN/AS

Photo Adam Mørk – courtesy of 3XN/AS

The Whirlpool – text by 3Xn Architects

Inspired by the shape of water in endless motion, Denmark’s new National Aquarium, The Blue Planet, is shaped as a great whirlpool, and the building itself tells the story of what awaits inside. The whirlpool concept originates in a narrative about water, and as an image, is at once both abstract and figurative. It stirs attention with its distinctive vortex blades, but at the same time, as a building, it changes dramatically depending on viewing angle, distance, and daylight conditions. From the air, almost entirely white, its contours are reminiscent of a starfish. From the front, the building’s organic lines are evocative of silvery-grey waves or a vast sea creature, and on closer inspection, the facade patterning is reminiscent of fish scales.
This is a building that invites interpretation.

Photo Adam Mørk – courtesy of 3XN/AS

 Flexibility
The Blue Planet is located on an elevated headland towards the sea, north of Kastrup Harbor. The building’s distinctive shape is clearly visible to travelers arriving by plane at the nearby Copenhagen Airport. The facade is covered with more than 33,000 small diamond-shaped aluminum shingles, which adapt to the building’s organic form. The whirlpool concept was chosen as ideal not only for its visual associations but also because it resolved a practical challenge in the design brief: it ensures that one or more of the whirlpool arms, with relative ease and without disrupting the building’s integrity or the operation of the aquarium, can be extended by more than 30 % to create more exhibition space.

Photos Adam Mørk – courtesy of 3XN/AS

The arrival and interior
Visitors reach the entrance by following the first and longest of the whirlpool’s arms, which already starts in the landscape. With a smooth transition, the landscape surpasses the building, while the outdoor ponds mark the unique experience that awaits the aquarium visitors as they enter: the whirlpool has pulled them into another world – a world beneath the surface of the sea.
A circular foyer is the center of motion around the aquarium, and it is here that visitors choose which river, lake, or ocean to explore. By enabling multiple routes, the risk of queues in front of individual aquariums is reduced. The interiors range from grand to intimate settings, allowing the architecture and the exhibits to jointly convey an array of diverse environments and moods.

National Aquarium of Denmark by 3XN Architects: Architectural model and conceptual diagram.Courtesy of 3XN Architects.

Photo Adam Mørk – courtesy of 3XN/AS

The curved ceilings of the aquarium are reminiscent of the baleen of a large whale. The exhibition is a total concept offering all visitors a sensuous and captivating experience of life in and under the water. A mixture of light, sound, advanced AV technology, projections, film, interactivity, graphics, illustrations, and signs aimed at all age levels ensures that every visitor, regardless of background or interests, has the best experience possible. As the only aquarium in Denmark, The Blue Planet focuses on all aquatic life – from cold and warm waters to fresh and salt. In total, The Blue Planet contains approximately 7 million liters of water and 53 aquariums and displays. The restaurant’s decor is based on the colors and expressions that characterize Nordic nature. The restaurant faces south-east and thus offers a panoramic view of the sea. The outdoor facilities include a terrace with seating, a pond with carp, and a tank with sea lions. The sea lions can also be looked at from the inside of the aquarium.

Photos Adam Mørk – courtesy of 3XN/AS

Construction and Location
The building extends beyond the original coastline, placing special requirements on the facility’s structures in a terrain with a tendency to subsidence; thus, its structure was founded on piles. The building’s architectural facade design forms the basis for the design of the steel structures. The load-bearing system consists of 54 unique steel frames, which, via their radial positioning and geometry, form the base of the curved facades. A service line was built 1.7 km out into the Øresund to obtain suitable water for the aquariums.
Moreover, the cooling system for aquariums and the climate system for public areas also use seawater. The Blue Planet has an outstanding location on the shores of Øresund, only eight kilometers from the Copenhagen City Hall Square.

 Photos, drawings, and images courtesy of 3XN/AS