This huge facility 6.3 kilometers long, which lies 50 meters underground, is one of the world's largest flood control channels. As this neighborhood forms a basin with several small rivers, a flood caused by heavy rains frequently occurred. The damage had gradually become serious because of urbanization. It was an urgent measure to build this facility at that time.
In case of heavy rain, the flooding water from the several small rivers is caught by four horizontal shafts of this facility to be conducted to the huge underground tank as shown in the picture. The water in this tank is slowly discharged to a nearby big river 'The Edo' to protect this vicinity from a flood. This underground tank 177 meters long features 670,000 square meters of water reserves, and is usually empty.
Licensed tour guide, travel consultant,