The Metropolitan Area Outer Underground Discharge Channel is the world largest flood alleviation establishment in Kasukabe, Saitama.
Completed building in June 2006, it discharges water into the Edo River during rain and typhoon seasons.
It consists of five vertical shafts with heights of 60 m and diameters of 30 m, connected by 6.3 km of tunnels, a giant water tank with 59 massive pillars, and 14000 h.p. turbines that can pump up to 200 tons of water into a river per second.
These are the pictures of the surge tank. As you can see, the high ceiling and the huge pillars make it look like an underground temple. The illusory space has been used for some films and music videos.
The establishment is open for visitors for free, but the tour guide offered there is only in Japanese. Non-Japanese speakers must have someone who understands Japanese for safety reason. The tour takes about 90 minutes and is held three times a day Tuesday through Friday.
Link: “The Metropolitan Area Outer Underground Discharge Channel Tour” (Japanese)
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