The Water Cube's outer walls are composed of over 100,000 square meters of ETFE pillows -- translucent cushions made from ethylene tetrafluoroethylene, each just 0.2 millimeters thick, roughly the thickness of a human hair doubled. Supplied and installed by Vector Foiltec, the ETFE cladding admits more light and heat than traditional glass, reducing the building's energy costs by 30 percent. The structure was also designed to capture and recycle 80 percent of the water that falls on its roof or evaporates from its pools. At night, the building glows blue, its bubble-patterned facade illuminated from within. Since 2013, an LED light show called "Nature and Man in Rhapsody of Light" has adjusted the building's colors based on trending emoji on Sina Weibo, using social media sentiment to calculate the collective "mood" of the Chinese public.

During the 2008 Olympics, the Water Cube hosted swimming, diving, and synchronized swimming events in a venue with a capacity of 17,000. Over the course of the Games, 25 world records were broken inside the building, earning it a reputation as the fastest Olympic pool ever built. The claim, however, comes with an asterisk: all but two of those records were set by swimmers wearing the LZR Racer bodysuit, a Speedo design so hydrodynamically efficient that FINA, swimming's governing body, effectively banned such suits in 2010. The pool's design did contribute to performance -- its deeper-than-standard depth and wave-absorbing lane dividers reduced turbulence -- but the suit controversy ensured that the 2008 records would be debated for years.

After the Olympics, the Water Cube faced the question that haunts every purpose-built Olympic venue: what comes next? The answer arrived in stages. A portion of the facility was converted into a 12,000-square-meter public water park, designed by the Canadian firm Forrec, featuring seven-story water slides and a wave machine. The facility reopened on August 8, 2010, the second anniversary of the Games' opening ceremony. By 2018, the venue was generating 124 million yuan in annual revenue and breaking even. Then came a second Olympic life: for the 2022 Winter Games, the Water Cube was transformed into the "Ice Cube," hosting curling events. The conversion required installing ice-making equipment and sophisticated climate control systems inside a building originally designed to keep water warm.

The Water Cube sits across from the Beijing National Stadium -- the Bird's Nest -- on the Olympic Green, and their pairing is deliberate. The cube represents earth; the elliptical stadium represents heaven. The juxtaposition echoes ancient Chinese cosmological symbolism, the same philosophy that shaped the square Temple of Earth and the circular Temple of Heaven centuries earlier. Together, the two buildings form a dialogue between tradition and modernity, between a civilization that has been thinking about the relationship between earth and sky for millennia and the twenty-first-century engineering that gives those ideas new material form. The Water Cube has won prizes from the Venice Biennale, Popular Science, and the MacRobert Award -- the UK's top engineering prize -- but its most lasting achievement may be proving that a building inspired by soap foam and ancient philosophy can host both summer and winter Olympic sports.