Passengers arriving by ferry or ocean liner in the French port of Le Havre have, for decades, satisfied the urge to step on the gas pedal and speed away. This ancient industrial harbor, along the English Channel, has long had a reputation as a dreary, gritty place. After the city’s devastation in World War II, it was rebuilt on a tight budget, largely by architect Auguste Perret, adhering to his famous dictum: “Concrete is beautiful.” Despite Perret’s talents, travelers—on trans-Atlantic crossings or en route between the U.K. and Paris or elsewhere on the Continent—rarely felt inspired to linger.

But that may be changing. With the city’s diminished role as a ferry transfer point since the Chunnel’s completion, and the obsolescence of its aging port infrastructure, Le Havre has been energetically reinventing itself. The current revitalization aims to transform some of France’s oldest docks into a leisure, cultural, and residential district, with both new construction and the adaptive reuse of low-lying warehouses.

On and near Le Havre’s historic Quai de La Réunion, once aromatic with coffee cargo, will be two anchor projects by Ateliers Jean Nouvel. The Sea and Sustainable Development Center, anticipated for 2010, will feature a 328-foot-tall tower, and exhibition spaces devoted to the historic, economic, and environmental significance of this maritime region. It will also house a meteorological station and a restaurant with panoramic views. But the architect’s companion project, Les Bains des Docks, directly across an inlet, is already finished, and with spectacular results—truly, as the French would say, a tour de force.

The $29 million Les Bains des Docks aquatic center, reimagines the concept of a public pool. On the exterior, the boxy precast-concrete shell, painted gun-metal gray, echoes the scale and simple massing of surrounding warehouses. Only the playful composition of rectangular apertures hints at an interior transcending the ordinary or functional.

Inside the front door and up a run of blanched terrazzo steps, the pure white interior—animated by daylight, water, and a quasi-Cubist composition of blocky three-dimensional forms—begins to reveal itself, and the effect is dazzling. Beyond the reception desk, atop the entry stairs, you catch your first oblique glimpse of a pool, behind glass. The ultra-white interior (flowing seamlessly into protected exterior spaces within the enveloping shell) features mosaic floors, ceilings, and walls of 20-by-20-millimeter (about 3⁄4 inch) vitreous tiles. These luminously translucent pâte de verre squares establish spatial continuity and a module for the 92,570-square-foot building: No tile was cut.

The same small-scale grid textures the exterior cladding, which Nouvel originally intended to leave pale and unpigmented. But prototype panels quickly convinced him “to accentuate the [exterior/interior] contrast, exploiting the particular and surprising light of Le Havre,” says Mirco Tardio, principal project architect. The resulting, dark-skinned monolith evokes a geode—its stony exterior hiding a partially hollowed inner realm, lined in geometric crystals.

The radiant, double-height reception zone leads to changing areas, equally white and bathed in sunlight, confirming the initial impression: Miraculously missing are the familiar traits of public pools—booming echoes; reeking chlorine; and grungy, windowless, institutional locker rooms. Instead, Nouvel took poetic inspiration from natural lagoons and Roman baths, offering myriad ways to experience water.

Once you’ve relinquished your shoes, suited up for swimming, and crossed the disinfecting-footbath threshold, you’re ready to explore the possibilities. Les Bains offers three major options: recreational pools, an aqueous spa, and dry cardio-fitness areas.

The sequence unfolds through spaces inhabited by water, light, shadow, and moving bathers. Water and swimmers flow from inside out and back again. An Olympic-size pool—open to the sky and surrounded by tiled decks and walls carved with cubic niches and apertures to the docklands—offers outdoor use year-round. (In winter, a warm-water channel wafts swimmers between indoors and out.) A waterfall, a superb hydro-massage, rushes into another outdoor pool.

Inside, following the Roman model, a dozen different options exist: hot and cold baths, whirlpools, saunas, a Turkish bath, fountains, sprays, soothing “rain,” turbulent jets, and pools spilling into one another. In the area for children and families, a hidden, tortuous slide offers an exhilarating plunge, while nearby, a veil of water surrounds a pool, and fine geysers shoot up from a floor. Here, the only splashes of color appear: wall, ceiling, and floor cushions resembling giant Starburst chews.

Nouvel’s team carefully limited reverberation. Glossy, stretched-fabric ceilings of varying heights mute noise, as does the blocky geometry, articulating intimately scaled areas. Mostly you hear sounds of water: trickling, gushing, roaring, trilling, or lapping.

Les Bains appeals simultaneously to the senses of sound, touch, and sight. Shafts of sunlight filter in, flicker off the water and shiny ceilings, and refract through the translucent tiles. (Nighttime illumination subtly glows from underwater or semihidden sources overhead.) Sight lines and apertures offer oblique views between pools, to the sky, or out to the dock and harbor. In this sanctum of serenity, you never lose touch with the outside world.

But lest you think you’ve died and gone to swimming heaven, a few glitches remain. Maintenance of all-white spaces poses obvious challenges—especially with 700 to 2,000 users daily. In high-traffic zones, not all underfoot grout is pristine, and some floor tiles have come loose. (Nouvel’s and the center’s teams are currently devising solutions.)

That said, the experience here is extraordinary—firmly anchored in Le Havre, yet luring you to float blissfully away.