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Deep beneath the ground in Kasukabe City, Saitama Prefecture, about 50 meters below the surface, lies a vast underground space. This is the pressure-adjustment water tank of the Metropolitan Area Outer Underground Discharge Channel, an area with a solemn atmosphere reminiscent of an ancient temple. The enormous chamber is 78 meters wide, 177 meters long, and 18 meters high, lined with 59 concrete pillars, each 18 meters tall and weighing 500 tons. The sight overwhelms visitors, making them feel as if they have wandered into another world. (city.kasukabe.lg.jp)
This underground temple is part of one of the world’s largest underground drainage systems, built to protect urban areas from flooding. When local rivers such as the Nakagawa, Kuramatsugawa, and Otoshikoritonegawa rise, excess water is channeled underground and discharged into the Edogawa River. Stretching 6.3 kilometers in total length, the channel was completed in 2006 and has since prevented many flood disasters. (ktr.mlit.go.jp)
This region has long suffered from flooding because of its low elevation and encirclement by large rivers. The rivers have gentle gradients, making it difficult for water to flow out quickly after heavy rain, so water levels remain high. Urbanization in recent years has further reduced the land’s ability to absorb rainwater, increasing flood risk. Against this backdrop, the construction of this massive underground drainage channel was planned. (ktr.mlit.go.jp)
Stepping into the pressure-adjustment water tank, visitors are enveloped in silence and cold air, confronted by a forest of concrete pillars. These pillars tower like those of an ancient temple, inspiring awe. The chamber was designed to reduce the velocity of floodwaters and ensure smooth flow, and its functional beauty creates a unique atmosphere. (city.kasukabe.lg.jp)
Because of its grand scale and unique atmosphere, this underground temple has been used as a filming location for movies, television dramas, and music videos. Its majestic appearance appeals to creators as an ideal setting for recreating fictional worlds in reality. (city.kasukabe.lg.jp)
General tours are also available—with advance reservation, it is possible to visit this underground temple in person. The tour offers insight into the facility’s role and mechanisms, providing a rare opportunity to experience the hidden side of massive infrastructure seldom seen by the public. (gaikaku.jp)
This underground temple represents the culmination of human wisdom and engineering, built to protect lives from the threats of nature. Setting foot in this grand space rekindles one’s appreciation for the coexistence between humans and nature, and for the sense of security brought by technological progress.