The “Underground Shrine” that Protects Tokyo from Flooding

Marvel at the size and scope of this cutting-edge disaster prevention facility, a must-see for urban exploration fans

The annual precipitation in Japan is about twice the global average, making it extremely important to reduce damage from inundation, especially in the Tokyo Metropolitan Area where the population is concentrated. Constructed underneath Route 16, a beltway in the Tokyo Metropolitan Area, the Metropolitan Outer Area Underground Discharge Channel is one of the largest underground discharge channels in the world. When the water level rises above the overflow banks of small and medium-sized rivers, the water flows into a big shaft (about 30 meters in diameter and 70 meters deep—large enough to hold the Statue of Liberty) and then through an underground tunnel (10 meters in diameter and 6.3 kilometers long) to reach the huge pressure-adjusting tank known as the “Underground Shrine.” From here, the water is drained into the Edogawa River using four of the largest pumps in Japan. These pumps are modified aircraft components driven by gas pistons that deliver 14,000 horsepower of output, and each one can pump 50 cubic meters of water per second. 

As you descend to the Underground Shrine, you will be astonished at the scale of its 59 oval stone pillars that stand 18 meters high, each weighing 500 tons. It looks like the ruins of a lost civilization. Your guide will shed light on how this giant facility protects the residents of the Tokyo Metropolitan Area from flooding. This lesser-known side of Japan must be seen to be believed.

The Metropolitan Outer Area Underground Discharge Channel