Kansai International Airport — Osaka, Japan

KIX rises from an artificial island built in Osaka Bay, an engineering undertaking that required leveling mountains for landfill and remains one of the most expensive airport construction projects ever completed when it opened in 1994. Architect Renzo Piano designed its main terminal as a single sweeping structure, at the time the longest airport building in the world, and the offshore site allows KIX to operate around the clock, unlike the noise-restricted, curfew-bound Itami airport closer to central Osaka. Subsidence proved a persistent challenge from the start, with the artificial island sinking into Osaka Bay's soft seabed faster than early engineering estimates predicted, requiring ongoing structural adjustments. In September 2018, Typhoon Jebi flooded large sections of the airport and a tanker collision damaged the connecting bridge, forcing a lengthy partial closure that tested the facility's resilience. KIX today serves as the main international gateway for the broader Kansai region encompassing Osaka, Kyoto, Nara, and Kobe.