A massive flood control facility for the Tokyo metropolis will open its doors to the public for tours starting mid-April.

The Metropolitan Area Outer Underground Discharge Channel, located in Kasukabe, Saitama Prefecture, north of Tokyo, is a facility that prevents flooding by drawing water from small and medium-sized rivers and discharging it into the Edo River downstream during heavy rain.

The underground space is lined with huge pillars and is also known as an “underground shrine.”

Although tours are held during normal times, the Kanto Regional Development Bureau will begin tours from the middle of April where visitors can actually enter areas that were previously closed to the public.

Officials hope that the new tour will encourage more people to visit and raise awareness of disaster prevention.

S/ Hidaka Mizuki, Nippon TV reporter: “The 30-meter-diameter vertical shaft is where water is poured in from the river, but it's very impressive when you look up.”

At present, the number of participants in the tours is around 60,000 per year, but they hope to increase this to 100,000 per year in the future.