The secret maze of the "Underground Temple" in Saitama

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At about 30 km north of Tokyo, in Kasukabe, a city of Saitama prefecture (part of the Greater Tokyo area) there is the world's largest underground flood water diversion infrastructure.[caption id="attachment_3355" align="aligncenter" width="300"]14095797450_136ef4371b Credit: qorokke.jp[/caption]The purpose of this facility, completed by early 2009, is to mitigate overflowing of the city's main waterways and rivers, especially during rain and typhoon season.How ? By draining and storing water from flooded residential areas into 5 concrete containment silos (gigantic tanks with diameters of 32 m and heights of 70 m) and a colossal pressure-controlled tank (supported by towering pillars weighing 500 tones each), to eventually discharge it into the Edo River thanks to a 6.4 km network of tunnels connecting the shafts (dug about 50 m below ground).[caption id="attachment_3350" align="alignright" width="301"]Credit: web-japan.org Credit: web-japan.org[/caption]This mammoth undertaking is a world-class architecture employing Japan's state-of-the-art civil engineering technologies, such as a mechanism using 7 810 MW pumps capable of dumping 200 tons of water at a maximum rate (equivalent to a 25-meter swimming pool) in no more than a second.If you decide to visit the "Ryukyukan" (the Underground Exploration Museum) offering free tours, you will have the chance to get an inside look at the tank structure, larger than a soccer pitch and resembling an “underground temple” with its 59 pillars.[caption id="attachment_3353" align="aligncenter" width="237"]Credit: commons.wikimedia.org Credit: commons.wikimedia.org[/caption]You will also obtain more technical details but remember that the tours are exclusively conducted in Japanese, and that it is compulsory to be accompanied by a native speaker (for security reasons) if you do not understand Japanese. There are two kinds of tours, one for a group of 6 people or less and one for 26 participants or more (to 50 people).Enjoy the visit !Metropolitan Area Outer Underground Discharge ChannelAddress: 720 Kamikanasaki, Kasukabe city, Saitama 344-0111Access:- By car:30 minutes' drive on Route 16 toward Noda, from Iwatsuki IC of Tohoku Expressway. (Approx.17km)40 minutes' drive on Route 16 toward Noda, from Kashiwa IC of Joban Expressway. (Approx.20km)- From train station:40 minutes' walk from North exit of Minami-Sakurai Station, Tobu Noda Line (Approx. 3km) or 7 minutes by taxi (about 1300 yen)Hours & Fees:- Free- Apply in advance of your tour date- Group of 26-50 people: 3 departs, every week, on Monday only (10:00 - 11:00 / 13:00 - 14:00 / 15:00 - 16:00)- Group of 1-6 people: 4 departs, every week, from Tuesday to Friday (10:00 - 11:00 / 11:00 - 12:00 / 13:00 - 14:00 / 15:00 - 16:00)Recommended season:No tour when facility is under construction or operated periodically (for schedule details, better to call in advance).Contact:048-746-0748 / 048 747 0281 (office opened from 9:00 to 16:30)

Sources:(1) http://www.ktr.mlit.go.jp(2) http://web-japan.org