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An Underground Wonder Protecting Tokyo

HOME > Japan’s Local Treasures > An Underground Wonder Protecting Tokyo

Go deep beneath suburban Tokyo to explore this marvel of modern engineering

Saitama Prefecture Products & Tourism Association

In Kasukabe, less than an hour by train from central Tokyo, is an underground engineering wonder built to save the city from flood damage which often occurred due to natural disasters such as typhoons. The official name of the tank and tunnel system is the Metropolitan Outer Area Underground Discharge Channel. Built from 1993 to 2006, this concrete tunnel system, about 6.3kms long, is also known as “The Underground Shrine”. About seven times a year, it diverts water from heavy rainstorms and keeps the streets of Tokyo from flooding. It is said that its construction has saved more than ¥140 billion yen in damage.

The facility is open to the public for guided tours which last around 50 minutes. To reach the system’s massive water collection tank you will need to descend around 100 steps. This cavernous subterranean space is 78 meters wide, 177 meters long (equivalent to the area of a soccer field), and 18 meters high. The tank is fortified with 59 giant concrete pillars necessary to support the ceiling and withstand the buoyancy from the groundwater. For those who want to know how the water drains, there is also a separate tour to see the huge propellers in the back of the tank, for which participants will need to wear rubber boots and a helmet with headlights.