"Renovation should tell the story of a historic building's past life." Dorte Mandrup-Poulsen, principal of Dorte Mandrup Arkitekter, expressed that philosophy through one of the firm's recent projects: the transformation of a 1921 seaplane hangar into the Denmark headquarters of Cell Network, a Scandinavian company specializing in Internet solutions and strategy.

Built as part of Copenhagen's Holmen naval base, the hangar was Denmark's first pre-stressed concrete structure of this size. It started out housing Heinkel reconnaissance seaplanes, later functioning as an artillery school and a military repair shop. Traces of former occupants—a lube pit, brick walls, wood-wool cement ceiling panels—still dotted the interior when Cell Network leased the landmark.

Shortly thereafter, Mandrup-Poulsen and her team swooped into action. They stayed true to the building's past, leaving the hangar shell virtually intact. The wooden roof and brick sidewalls remain. So does the glazed front facade, its wooden frames now repainted white and an inner layer of glazing added for insulation. Existing skylights were kept, too, just updated with polycarbonate. The existing concrete construction—a series of beams supporting the roof—was left alone as well.

When the hangar was still operational as such, the back of the building had featured sliding wooden doors that opened to let planes in and out. A previous renovation replaced the doors with a plywood wall. Mandrup-Poulsen discovered their existence from old drawings and reincarnated them as steel-and-aluminum double doors mounted on a steel track. In warm weather, the building's rear now opens to the air.

At the side of the lofty 8,000-square-foot interior was the lube pit that the Danish military had cut in the concrete-tile floor to facilitate the greasing of tank parts. Rather than fill in the 66-foot-long, 21/2-foot-wide trench, Mandrup-Poulsen created a glowing "canal" through the new birch-plywood floor by installing blue fluorescent tubes in the hole and covering it with 11/2-inch float-glass panels. "Before this site was established on landfill in 1919, it was the sea. The canal is an abstract representation of water," she says.

The architect then turned to operational necessities: workstations for 150 employees, formal and informal meeting zones, video-presentation capabilities, an employee canteen, and updated rest rooms. Finally, since the company often rents the space to magazines for photo shoots, a flexible area was needed for special events.

The hangar's 36-foot-high vault allowed Mandrup-Poulsen to propose a dramatic solution, three interior towers of steel and birch, partially enclosed by glass. "The towers achieve spatial diversity with a simple composition and create dynamism and movement," she says. A triple-tier tower is mostly devoted to work space. Birch-topped custom workstations for more than 100 employees occupy two levels; executive offices are on the ground and second floors. Steel staircases handle vertical circulation.

A glazed conference room is on the ground level of a two-story tower, next to a pool of actual water. Furnishings are by Charles and Ray Eames, with Aluminum Group chairs and a table topped in plastic laminate. The second level resembles a roof terrace, surrounded by white-painted steel railings. Custom cotton-covered beanbag chairs beckon employees to sit and relax. "A welcome contrast to the fast-paced nature of Web design," says Mandrup Poulsen, who also added Jasper Morrison's Glo-Ball floor lights.
In the tallest tower, four stories high, Glo-Balls accompany Morrison's Low-Pad chairs in a ground-level guest lounge. At its center, built into the floor, a faux hearth glows orange from more fluorescents under laminated float glass. On the second and third levels, Eames tables and additional Low-Pad chairs outfit meeting rooms. The fourth level is another roofless meditation space, this one offering hammocks strung between steel posts.

Mandrup-Poulsen positioned the towers to form a central court—further delineated by the 28-foot lengths of white parachute fabric that she hung from the tops of the towers and from additional 30-foot-high steel structures. The fabric helped the architect meet her client's flexibility requirements for special events. "It allows the size of the space to be altered quickly and easily, reflects daylight, and regulates acoustics," she says. Furthermore, when drawn taut, the fabric becomes a screen for video presentations.

The architect didn't forget downtime either. At the back of the building, a red Verner Panton sofa seats eight for informal discussions. For the adjacent staff canteen, Mandrup-Poulsen paired custom MDF tables with Peter Karpf's plywood Nxt chairs as well as custom MDF communal counters with Morrison's Hi-Pad chairs as bar stools. When the steel-and-aluminum double doors slide open, the staff gets access to a deck of oiled larch wood—and a glimpse of modern-day airplanes en route to Kastrup airport.