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Metropolitan Area Outer Underground Discharge Channel

Published: Aug 11, 2026

Updated: Aug 11, 2026

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Representative image — not a photograph of this location.

Fifty metres under a football pitch in Kasukabe is a concrete hall 177 metres long and 78 wide, held up by 59 pillars each weighing 500 tonnes. It is a pressure-regulating tank: when the rivers north of Tokyo flood, water is dropped down five shafts, buffered here, and pumped into the Edo river by turbines rated at 200 cubic metres a second. It is the largest facility of its kind in the world and it exists because this basin used to flood every few years.

Everyone calls it the underground temple, and the resemblance is not accidental — the pillars are on a grid and the lighting is uplit from the floor. It has been used as a film set often enough that people recognise it before they know what it is. Tours run daily and must be booked; the surface visitor centre with the working control room is free and needs no reservation.

Essential Information

Opening Hours

Tours run daily by advance booking | Ryu-Q-kan exhibition room open without reservation — confirm current hours

Closed: Tours are suspended during heavy rain when the facility is operating — confirm on the day

Entrance Fee

¥1,200 for the Underground Temple tour (about 55 minutes) | ¥1,500 with lighting effects | ¥5,500 for the 110-minute pump and drainage route | Free entry to the Ryu-Q-kan exhibition room

Best Season

Year-round | Winter and dry spells, when operational closures are least likely

Visit Duration

1.5–2 hours including the tour and the exhibition room

Getting There

Access Information

Kamikanasaki 720, Kasukabe City, at the Ryu-Q-kan visitor centre. About 40 minutes by car from central Kasukabe; about 40 minutes on foot from Minami-Sakurai Station on the Tobu Noda Line. The Underground Temple tour runs about 55 minutes, takes 55 people and costs ¥1,200 per person; a version with lighting effects is about 55 minutes at ¥1,500; a longer route covering the pumps and drainage plant is about 110 minutes for 20 people at ¥5,500. All tours must be booked in advance. The Ryu-Q-kan exhibition room is free and needs no reservation.

Insider Guide

Premium

**Book before you travel.** Tours sell out, particularly at weekends, and turning up without a reservation gets you the free exhibition room and nothing else. **It is 116 steps down and the same back up.** No lift on the standard route. This is the practical constraint that catches people out. **Tours are cancelled when it rains hard.** The tank is operational infrastructure. If it is doing its job, nobody is going in it. Check on the morning of a wet day. **The pillars are compression, not decoration.** Each weighs 500 tonnes and they are there to stop the tank floating upward on groundwater when it is empty. Knowing that is the difference between a photo opportunity and understanding the building. **The Ryu-Q-kan control room is free.** Upstairs, with the live river gauges and the operators' desks. Worth twenty minutes even if you cannot get a tour place. **It has run more than a hundred times since 2006.** This is not a monument to a flood that might come.

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