Practical Guide

Visiting the "Underground Temple": A Guide to Tours of the Metropolitan Area Outer Underground Discharge Channel

Published: 2026-10-03

A vast underground hall lined with 59 pillars: the pressure-adjusting tank of the Metropolitan Area Outer Underground Discharge Channel. Anyone can enter this "underground temple" by joining a guided tour, but tours must be booked in advance and there are rules on age and clothing. Here is what to know before you go, based on the official information.

The "Underground Temple" Is a Flood-Control Facility

The Metropolitan Area Outer Underground Discharge Channel is a national flood-control facility in Kasukabe, Saitama. When heavy rain swells the small rivers in the area, it takes in their water and carries it through a tunnel about 6.3 kilometers long and about 10 meters across, running some 50 meters beneath National Route 16, and releases it into the Edo River. The whole system was completed in 2006. Its pumps can discharge up to about 200 cubic meters of water per second, roughly a 25-meter swimming pool every second.

The part called the "underground temple" is the pressure-adjusting tank, a huge pool that slows the water arriving from the tunnel. The space is 177 meters long, 78 meters wide and 18 meters high, with 59 pillars. Each pillar is said to weigh about 500 tons, and they also act as weights that keep the tank from being pushed up by groundwater.

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Tours Are Booking-Only, Opening One Month Ahead

Tours can only be joined with an advance booking; same-day bookings are not accepted. Individual bookings open on the same date one month before your visit: from midnight on the official website, or by phone (048-747-0281) from 9:00 to 16:30. The day before, you can book online until 23:59 or by phone until 16:30. Groups can book from the same date six months ahead, by email, first come, first served.

Cancellations and date changes are free up to three days before. From two days before, even a change of date costs the full fee. Popular days fill quickly, so once you know your date, booking on the day reservations open is the safest approach.

Choosing a Course: Every Course Enters the Underground Temple

There are seven courses, and all of them take you into the underground temple (the pressure-adjusting tank). The simplest is the Underground Temple Course: about 55 minutes and 1,200 yen per person. After an introduction in the first-floor lobby, you go down into the tank and have some free time to look around.

For more, the Shaft Experience Course (about 110 minutes, 3,500 yen) walks the service catwalk of the First Shaft, about 70 meters deep, and the Pump Course (about 110 minutes, 5,500 yen) takes you to the giant pumps and gas turbines. Other courses include walking an underground channel, an evening course with sound and light, and a disaster-prevention course built around a game. Course content and prices can change, so check the official website before booking.

Who Can Join, and What to Wear

For safety, children who have not yet started elementary school cannot join, even with an adult. Participants of junior-high age or younger must be accompanied by an adult, up to five children per adult. Every course involves about 100 steps up and down with no elevator or escalator, so you need to be able to walk unaided. Guidance is in Japanese only, and pets and anyone who has been drinking are not allowed.

Inside the tank it is around 20°C even in midsummer and around 10°C in midwinter, so bring a layer even in summer. Floors and stairs are wet, slippery and dark in places; high thin heels, beach sandals and backless shoes are not allowed. Wear comfortable sneakers you do not mind getting dirty. There is no toilet break during the tour, so go before it starts.

Rainy Days, and After the Facility Has Been in Operation

Tours usually go ahead in the rain. But when the facility is actually operating during heavy rain, the course changes: instead of going down into the tank, you view it from the service catwalk. There is no change in price or refund when the course changes.

After water has flowed in, cleanup and inspections are needed, so the tank and shafts stay closed for about a week afterwards. If your visit is just after a typhoon or heavy rain, check the official website and the emails you receive.

Getting There: The Nearest Station Is Minami-Sakurai

Check-in is on the first floor of the Ryu-Q-Kan building on the site (720 Kamikanasaki, Kasukabe, Saitama). Check in at least 10 minutes before your tour starts. The nearest station is Minami-Sakurai on the Tobu Urban Park Line. A community bus, the Kasukabe "Haru Bus," leaves from the north exit, but it runs only on certain days and times and not on Sundays.

There are no taxis waiting at Minami-Sakurai, so call a taxi company before you set off; the ride takes about 10 minutes. Taxis are usually available at the east exit of Kasukabe Station, about 20 minutes away. By car, there is free parking for about 50 vehicles.

The Underground Temple as a Liminal Space

What makes the underground temple strange is not just its size but that, most of the time, it is a space meant for no one. It exists only to catch water in a flood, and on a clear day the endless rows of identical pillars simply wait in silence. During free viewing time, look down a line of pillars into the distance and you will see a still, almost human-free scene where time seems to have stopped.

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Photography is allowed during the tour, but take care not to capture other visitors. If you like long passages and vast underground spaces, the passage to the Keiyo Line platforms at Tokyo Station and Higashi-Narita, the former Narita Airport station, appear in "Liminal Spaces in Tokyo" and "Liminal Spaces in Kanagawa, Chiba and Saitama."

FAQ

Can I visit the underground temple without a booking?

No. Tours are booking-only, and same-day bookings are not accepted. Individuals can book from the same date one month before their visit, online or by phone.

Which course is the easiest?

The Underground Temple Course: about 55 minutes and 1,200 yen per person, with an introduction followed by a visit to the pressure-adjusting tank. Prices and courses can change, so check the official website.

Can children join?

Children from elementary-school age can join. Younger children cannot, even with an adult. Participants of junior-high age or younger must be accompanied by an adult, up to five children per adult.

Can I take photos?

Yes, photography is allowed during the tour. Please take care not to capture other visitors.

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