Metropolitan Area Outer Underground Discharge Channel

The abbreviation G- Cans denotes the Shutoken Gaikaku Hōsuiro (Japanese首都 圏 外 郭 放水 路, dt about " external drainage channel for the capital area," engl. Metropolitan Area Outer Underground Discharge Channel), the world 's largest underground drainage and sewerage system under the National Road 16 in the town Kasukabe in Saitama prefecture north of Tokyo.

It should buffer the mainly occurring during the passage of typhoons amounts of water and discharge controls. Construction began in 1992 and lasted 15 years, the cost of construction amounted to more than 2 billion euros.

At a depth of 50 m below the surface, five huge caverns of concrete cover with a height of 65 meters and 32 meters wide. With its 59 mighty buttresses form these underground water storage gigantic halls, reminiscent of the architecture of cathedrals. More than 60 km of underground tunnels with a diameter of up to 10 meters, the five concrete bucket. Since even these huge water reservoir can come to the edge of their capacity by the heavy rains and associated flooding, provide a pump system for the removal of water in the river Edogawa, which empties into the Pacific Ocean. With a pump capacity of 14,000 hp can be pumped out of the city into the river in this way 200 tons of water per second.

During the dry season the underground water storage attract large groups of tourists who want to see the impressive architecture up close.