Explore the great underground near Tokyo!

The metropolitan city, Tokyo. I guess it looked much bigger to you than you might have thought if you have visited this unique city.


Not only on the ground, also in the underground there are many city functions. I also ever heard of some urban legends that Tokyo has mysterious underground routes, etc. Anyway, the word “underground” may have a magical power to attract people.


Now I won’t talk about a mystery but I would like to show you the popular spot among Japanese nowadays, which really exists and it is called The Metropolitan Area Outer Underground Discharge Channel, the biggest drainage system in the world.


(Image from: https://ja.wikipedia.org/wiki/%E9%A6%96%E9%83%BD%E5%9C%8F%E5%A4%96%E9%83%AD%E6%94%BE%E6%B0%B4%E8%B7%AF)

1 tank

This giant facility stands for the Japan’s high technologies and flood control history. This huge tank in the image above is so called “The underground Parthenon shrine”, as it looks like the Parthenon in Greece with magnificent 59 pillars (weight: 500t / pillar).


1) Fighting against water

Japan is rich in water and green, surrounded by the sea and has various rivers inside. However, this country has also suffered from many flood damages. It is said the flood control history began in before Christ.


In 2006, this huge underground system was constructed to solve the flood problem in the east Tokyo and south Saitama area where there are several rivers, some are long and others are short. In addition the ground level is lower than other areas.


As shown in the image below, you can see there are many rivers spreading in the small island like veins of a leaf.)

(Image from: https://teachme.jp/contents/9022)

2 rivers

2) How does the system works?

Once it rains heavily, the surplus water in each small river is collected in small tanks. And then all the water comes to the huge tank (Length: 177m, width: 78m, height: 18m), passing through the tunnel of 6.3 kilometers that exists 50 meters below the ground. Look at the image below which shows how the giant drainage system works)


(Image from: http://terraoko.com/?p=75996)


When the massively collected water comes to the certain level in the huge tank (final stop), the four giant pumps let it out to the Edogawa, one of the large rivers in Tokyo area (shown in the left side of the image above). That is how the residential area nearby is protected from the flood damage. Each pump can drain 200 m3/second at maximum, which is equivalent to a 25-meter-long swimming pool.


How many times the drainage system works per year? The answer is 8 times approximately. Especially in the typhoon season, this facility gets busier. According to the record, water 19,000,000m3 was washed away into the Edogawa, taking four days, which is equivalent to 15 times the capacity of a baseball stadium.


(Image from: http://komekami.sakura.ne.jp/archives/956/pb159617)


If you are interested in, you can find information about the tour below.

Access: Get off a train at Minami-Sakurai Station on Tobu-Noda line, and take a bus to get off at bus stop “Ryukyukan” (龍Q館). (Or 30 to 40 minute-walk from the station to the facilities.)

Booking: Required (Web site or telephone).

Entrance fee: Free

Open: Thursday to Friday (except national holidays)

After heavy rain, the huge water tank is closed due to filled water. Tour may be cancelled or modified with limitations of visitors because of the construction, the facilities’ operation or weather condition. Also it is closed when it is filled with water. Even if it is fine on your visit day, it can be closed when it rains on the previous days. Please check the official web site beforehand.


Requirements to visitors:

– There are 100 steps between the ground and the bottom floor of the huge water tank (Without an elevator), so you are required to walk by yourself.

– You should arrive at the reception by half an hour before the tour starts.

– For the security, children under seven years are not allowed to visit even if accompanied by adults. Children from 7 to 12 years old must be accompanied by adults. (Up to five children per an adult)

– Tour is performed only in Japanese. If you don’t speak Japanese, you will need to attend with an interpreter.


Enjoy and explore!


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