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SANAA’s facility (1) replaces a 1964 gymnasium by Kenzo Tange (2) on a different site. Photos © Ken’Ichi Suzuki (1), Naomi Pollock (2), click to enlarge.

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Much bigger in size and scope than Tange’s gym, SANAA’s building occupies a 30-year-old landfill parcel in the heart of the city. Facing the Seto Inland Sea, this previously empty plot is walking distance from Takamatsu’s central train station as well as its ferry port. From there, boats make the transit to Japan’s mainland, Honshu, as well as the art island, Naoshima, where the SANAA-designed terminal welcomes visitors. While ferry passengers enjoy splendid sightings of the arena from the water, SANAA’s architecture enjoys unimpeded access to the ocean.

Initially the competition brief called for a place to host amateur athletic competitions. After SANAA’s victory, however, the program was enlarged to include a separate space for professional sports, pop music concerts, and other festivities. “Normally these requirements would result in a big building that people cannot walk through,” observes project architect and SANAA partner Rikiya Yamamoto.

This time the designers responded with an airy complex composed of three discrete pavilions—the 10,000-seat (5,000 fixed plus 5,000 movable) main arena for headliner events, the 1,000-seat sub-arena for local sports competitions, and the 330-seat budo for traditional martial arts—interspersed with open space. At street level, people are free to move in and around the parklike setting 24 hours a day. The three volumes are unified by the continuous wavy roof overhead and the communal basement below. “Everything under one big roof was an important concept,” explains Yamamoto. Contiguous with the arena floors, the shared lower level holds support functions, including locker rooms, training facilities, storage, and offices, plus their connecting underground passage.

With three arenas sheltered under one roof, the public is free to move through the new complex and its parklike setting 24 hours a day. Photo © Ken’Ichi Suzuki

Though a garage is incorporated into the main arena’s lower level, the whole pedestrian-friendly complex is an easy walk from the city center or the seaside boardwalk. From either direction, a paved slope ascends to the covered plaza in the middle of the facility. It is flanked by the primary entrances to the main arena and the sub-arena that leads to the boxy budo beyond.

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A paved slope (3 & 4) ascends to a covered plaza and the primary entrances to the main and sub-arenas. Photos © Ken’Ichi Suzuki

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Usually, indoor sports venues are sealed off from their surroundings, but, here, the relaxed, informal atmosphere outside permeates each volume. Ringed with windows, the sub-arena admits daylight from all directions. The main arena’s exterior is substantially glass, and its interior is barely divided at all, with fluid boundaries between circulation and spectator areas. “Inside, we didn’t want to make walls,” explains Sejima. What they did make was highly flexible space with a strong connection to place.

Measuring 381 feet in diameter, the main pavilion is essentially one enormous circular room capped with a dome (integrated with the overall roof) and centered around an oblong playing area. This core is surrounded by a band of circulation wide enough for concessions, or workshops and other small gatherings. The only vertical division between the two is the partial-height banks of spectator seating—tiers of blue, green, and yellow chairs overlooking the action. And even these are punctuated by generous passageways. Without barriers behind the stands, the roar of cheering fans fills the entire building, and the changing natural light, the water’s variable color, and the intense blue sky characterizing the area are perceptible throughout.

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A circulation zone (5) surrounds the main arena playing area (6). Photo © Ken’Ichi Suzuki

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The concrete floor in the main arena was also an important consideration: it had to be sturdy enough for the delivery trucks that drive directly inside. Highly adaptable, it can be topped with a temporary maple floor for basketball or outfitted with a stage when headliner bands pull into town. A mini-version of the main arena, the circular 236-foot-diameter sub-arena centers around its rectangular competition area, while the floor of the smaller budo can be cushioned with tatami placed on top of the wood floor for judo and kendo matches.

A mini-version of the main arena, the circular 236-foot-diameter sub-arena centers around its rectangular competition area. Photo © Ken’Ichi Suzuki

For traditional Japanese martial arts, the budo’s wood floor can be covered with tatami. Photo © Ken’Ichi Suzuki

Of course, the ceilings were even more challenging than the floors. Getting the height needed for high-flying sports like basketball and volleyball required a bit of juggling. Yet the architects wanted to keep the entire project as low as possible, to diminish its overall impact and preserve the neighbors’ waterfront views. “I didn’t want to separate the city from the sea,” states Sejima. They balanced these conflicting needs by raising the ground level slightly and then sinking the playing floors below grade. This strategy reduced the visible building mass yet still allowed for the main arena’s maximum ceiling height of 92 feet, the high point of the entire complex. Painted white, its surface is crisscrossed with catwalks holding the multitude of suspended lights needed to illuminate the venue’s wide range of activities.

Another height-saving measure was the remarkably thin construction of the colossal three-dimensionally curved roof. “It’s more like a skin,” says Yamamoto. Minimizing its depth, the roof is supported by a single truss system stretching from one end of the complex to the other (with a seismic joint for earthquake protection between the two larger venues).

Above the main arena, the exposed trusses read as a lattice of steel H-beams arranged in a 20-foot grid. This is secured by a hefty 3-foot-diameter hollow tension ring that is propped up by 16-foot-tall, 20-inch-diameter columns. These 32 hollow supports transfer their load to the 131-foot-deep piles. Manufactured by a steel fabricator in Fukuoka, the tension ring arrived in segments that were assembled on-site. “Normally, welding overhead is difficult, but robots can weld in any direction,” comments Yamamoto. While a smaller lattice and tension-ring system was used for the sub-arena, Vierendeel trusses top off the budo. Outside, the entire roof is clad with standing-seam stainless steel painted pale gray to protect it from corrosion and prevent its gleaming surface from disturbing nearby office workers.

In terms of function and capacity, Takamatsu had clearly outgrown the Tange gym. Nonetheless, one is still left wishing that Japan would find ways to fortify and repurpose its old and aging architectural treasures. In the Anabuki Arena Kagawa, however, the city gets so much more than a straight up athletic facility. It is a responsible urban gesture, an enticing public gathering place, and, as such, an important model for the future.

Click graphics to enlarge

Click graphic to enlarge