Tokyo, with a population of 12.4 million, is one of the largest cities in the world and still growing. It is known for not only having huge amounts of anime and robot fans, but also for its annual rainy and typhoon seasons that can flood the whole city. Because of this, there is a need to build a massive underground drainage system to counter the problem. In 1992, a plan called G-Cans Project or the Metropolitan Area Outer Underground Discharge Channel (drainage system) was approved and construction began. The G-Cans project was completed in 2004. Below are some of the pictures of “Tokyo’s Drainage System: The Largest in the World”.

Fototerra Finaldarkworld had a bit more to say:

To download of rain water, the complex is equipped with a turbopump 59. Their total capacity of 14 thousand horsepower, they can outrun the top 200 tons of water per second. It seems that this might certainly be designed for the most intense flooding. However, in this area in a heavy downpour falling on 200 millimeters of precipitation, and sometimes up to 400 (monthly rainfall for Moscow, for example, is 35 millimeters). Therefore, margin of safety facilities placed enormous. Let all the sea would rise in clouds and rain fall. Designers should consider a set of massive underground storage for many thousands of tons of water to the height of precipitation area upstairs is not to submergence.

Since its opening, the G-Cans has prevented floods from entering the metropolis, but “unfortunately” it can’t prevent many people, including celebrities and film makers from flooding the place. It is due to the G-Cans project is also meant to be a tourist attraction, and can be visited for free twice a day, from Tuesday to Friday. Unfortunately, the tour is conducted only in Japanese. My suggestion is you should learn the language; it is very interesting. If you would like to see more amazing tourist details and pictures of Japan’s G-Cans see Japan Underground Temple Tour (Pick Summary in English).