I've found this
link in a Spanish forum. Look at those pics, guess what it is. It's the Tokyo's subsoil
They're a tunnel system of 64 km and silos with a height of 65 m.
According to this other
link it's a project called G-can and it was started 12 years ago. The mission of this enormous "sewers" is to provide Tokyo's subsoil with the capacity of store big quantities of water in order to avert floods because monsoons and tidal waves :O Suuugoi desu ne~ :O It's great >o<
BTW, the pics have reminded me of some videogames sceneries hehe.
This one and
this one are sooo Silent Hill xD