The , is an underground water infrastructure project in Kasukabe, Saitama, Japan. It is the world's largest underground flood water diversion facility, built to mitigate overflowing of the city's major waterways and rivers during rain and typhoon seasons. It is located between Showa and Kasukabe in Saitama prefecture, on the outskirts of the city of Tokyo in the Greater Tokyo Area. Work on the project started in 1992 and was completed by early 2006. It consists of five concrete containment silos with heights of and diameters of , connected by of tunnels, beneath the surface, as well as a large water tank with a height of , with a length of , with a width of , and with fifty-nine massive pillars connected to seventy-eight pumps that can pump up to of water into the Edo River per second. See also Tunnel and Reservoir Plan (in Chicago) Basilica Cistern (in Istanbul) Underground Construction Stormwater Sewerage References External links (including photos) Aqueducts in Japan Buildings and structures in Saitama Prefecture Flood control projects Flood control in Japan Geography of Saitama Prefecture Macro-engineering Science and technology in Japan Tourist attractions in Saitama Prefecture Water tunnels Drainage tunnels Tunnels in Japan