KAI Copenhagen: Kengo Kuma's Harbor Bathhouse Opens Dec. 5

Copenhagen’s harbor is clean enough to swim in, and the city has spent years turning its old industrial waterfront into public space. On December 5, that transformation gets a new landmark. KAI, a public Water Culture House by the Japanese practice Kengo Kuma & Associates, opens on Paper Island (Papirøen) in the inner harbor with ten indoor and outdoor pools, three saunas, a cultural program and direct access to the water, all in one 5,800-square-meter (about 62,400-square-foot) building. For travelers planning a winter trip, it is a new reason to pack a swimsuit.

An Idea That Came From Copenhageners

KAI started with residents. In 2015 the City of Copenhagen ran an ideas competition for a new cultural and leisure facility on Paper Island and received 160 proposals, most of them asking for somewhere to swim that could double as a place to unwind and a base for local clubs. An international architecture competition followed in 2017, and a unanimous jury picked Kengo Kuma & Associates, The Copenhagen Post reported at the time. Cornelius Vöge Atelier for Architecture worked with the studio through the concept stage, Vilhelm Lauritzen Architects served as executive architect from detailed design to completion, and MT Højgaard was the main contractor. Copenhagen’s lord mayor, Sisse Marie Welling, says the city needs more places to swim and hopes KAI becomes a gathering point for residents and visitors who love the water.

The building cost DKK 989 million, with DKK 443 million from the City of Copenhagen and DKK 546 million from the Danish foundation Nordea-fonden, according to Wonderful Copenhagen. The funding also made room for a ground-source heat pump system, ten boreholes drilled 250 meters (about 820 feet) deep, that warms the outdoor pools all year. Henrik Lehmann Andersen, chief executive of Nordea-fonden, said he sees KAI as a potential new symbol for the city.

Five Brick Towers on the Water

Seen from the harbor, KAI is a cluster of five peaked brick towers that appear to float above a light glass base, their points rising beside the pyramid-roofed apartment buildings that now share the island. Each tower is shaped by the outline of the pool beneath it, and the tallest holds the Culture Tower, with rooms for culture, movement and the city’s clubs and associations. Some 300,000 handmade bricks clad the exterior, and 403 windows frame views of the city while drawing daylight inside.

The name works in two languages. In Japanese, kai refers to the sea; in Danish, it echoes kaj, the word for quay, a nod to the building’s place on Paper Island’s harbor edge. The project also deepens Kuma’s ties to Denmark: his studio designed H.C. Andersen’s House in Odense, which opened in 2021, with partner Yuki Ikeguchi in charge. Ikeguchi is also KAI’s lead architect.

“…a civic institution dedicated to water and community…” Yuki Ikeguchi, lead architect, Kengo Kuma & Associates, in the opening announcement

Ten Pools, Three Saunas and the Harbor

The pools are spread over two floors, each kept at its own temperature, so a visit plays out more like a circuit than a lap session.

Ground floor: a 25-meter fitness pool (27°C/81°F), a teaching pool (29°C/84°F) and three children’s play pools (32°C/90°F). According to KAI, children under 7 with a paying adult swim free on this floor.
Wellness, first floor: a therapy pool (36°C/97°F), a hot pool (42°C/108°F) and a cold plunge (15°C/59°F).
Outdoors, first floor: the Valley Pool (26°C/79°F), set between the brick towers and open to the sky in sun, rain or snow, and the Onsen (36°C/97°F), with views across the harbor.
In the harbor: a 50-meter swimming zone facing Opera Park and a plunge zone in front of the building, looking toward the Royal Danish Playhouse, both reached from a timber boardwalk.

Three saunas and a steam bath round out the facilities. Together the ten pools hold about a million liters of water, and the building has room for 380 bathers at a time. One caveat for early visitors: the harbor swimming areas will not be finished by December 5. The city expects them to open in early 2027, after which the timber deck and harbor bath are planned to stay open around the clock, all year.

Planning a Visit

KAI opens on Saturday, December 5, at noon, with an open house until 6 p.m. and free admission throughout the building, according to KAI’s website. Regular hours begin the next day: 6 a.m. to 9 p.m., seven days a week. Admission is priced in line with Copenhagen’s other municipal pools. Swim tickets are bought online, and machines at the entrance print a wristband when you scan your personal QR code; some cultural events need a separate ticket.

No food or drink is sold on site, though there are cafés nearby. The building has elevators between floors, accessible changing rooms and lifts into all the pools. With capacity capped at 380 bathers, build some flexibility into your plans during the opening weeks, and check the website for the cultural program, which is built around water both inside the pools and along the harborfront.

KAI’s address is Papirøen 47 in central Copenhagen. Paper Island sits across the water from Nyhavn, and the car-free Inner Harbour Bridge (Inderhavnsbroen), which links Nyhavn with Christianshavn, makes the crossing a short walk or bike ride.

Make a Day of It

Christopher Røhl, Copenhagen’s mayor for culture, leisure and citizen services, places KAI alongside Islands Brygge, the Black Diamond and the Opera House as one of the landmarks that bring Copenhageners to the harbor. A simple plan for a winter day on the water:

Swim early: start in the Valley Pool, then move to the Onsen for the harbor view.
Eat across the water: KAI sells no food, so walk over the Inner Harbour Bridge to Nyhavn for lunch.
Stay on the waterfront: the Opera House and Opera Park are close by, and the Royal Danish Playhouse faces KAI across the harbor.
Pick your moment: go on December 5 for the free open house, or wait for a weekday morning once regular hours begin.

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