To avoid floodings on typhoon season, the city of Saitama in Japan features an impressive storm sewer system. Its construction started in 1992, and its composed by giant concrete silos (65m tall, 32m wide) connected by 6.4km of underground tunnels 50m below the surface. It also has a giant tank: 25.4m tall, 177m long and 78 wide, with 59 concrete columns.
This impressive structure is opened for tourists. More pictures and videos below. Be sure to check out the truck being lifted through the sewer!.