Tokyo's gigantic flood prevention system

The pressure-controlled water tank at the Metropolitan Area Outer Underground Discharge Channel in Kusakabe, north of Tokyo. The facility, which is believed to be one of the largest facilities in the world, is composed of giant concrete containment silos (65m tall, 32m wide), connected by 3.97 miles of underground tunnels 50m beneath the surface as well as a large water tank called the "Underground Temple" which is 25.4m tall, with a length... more 

The pressure-controlled water tank at the Metropolitan Area Outer Underground Discharge Channel in Kusakabe, north of Tokyo. The facility, which is believed to be one of the largest facilities in the world, is composed of giant concrete containment silos (65m tall, 32m wide), connected by 3.97 miles of underground tunnels 50m beneath the surface as well as a large water tank called the "Underground Temple" which is 25.4m tall, with a length of 177m and 78m wide, with 59 concrete pillars.

(Photo: REUTERS/Ministry of Land, Infrastructure, Transport and Tourism-Edogawa River Office/Handout) less