Guide to Metropolitan Area Outer Underground Discharge Channel!

Located in Kasukabe City, Saitama Prefecture, Japan, the Metropolitan Area Outer Underground Discharge Channel is world-renowned as one of the largest underground flood control facilities, affectionately known as the Underground Temple.
Combining the overwhelming spatial beauty of its surge tank—where massive pillars stand like a forest—with state-of-the-art civil engineering, this facility has drawn international acclaim as a premier destination for disaster prevention infrastructure tourism.
This article provides a comprehensive overview of the facility's vital role, along with detailed guides to seven immersive tour routes that international visitors can fully enjoy.

1. What is the Metropolitan Area Outer Underground Discharge Channel?
2. 7 Tour Routes Suitable
   • Underground Temple Course: Step into the Pressure-Adjusting Water Tank
   • Shaft Experience Course: Exploring Shaft No. 1
   • Pump Conquest Course & Pump Mastery Course
   • Impeller Exploration Course: Get Close to Massive Drainage Machinery
   • Adventure Course: Walking Through Underground Tunnels
   • Minecraft Disaster Prevention Learning Course
   • River Basin Disaster Prevention Light-Up Course: A Nighttime Transformation
3. How to Book a Tour: Reservation Steps for Individuals and Groups
4. Future Plans and Disaster Prevention Tourism
5. Summary

1. What is the Metropolitan Area Outer Underground Discharge Channel?

The Metropolitan Area Outer Underground Discharge Channel is one of the world's largest underground floodways.
It diverts floodwaters from small and medium-sized local rivers into a 6.3 km underground tunnel network, discharging the water into the Edo River and significantly mitigating flood risks in the Tokyo metropolitan area.

The primary highlight of the facility is the Pressure-Adjusting Water Tank, a cavernous subterranean space measuring 78 metres wide, 177 metres long, and 18 metres high.
Its 59 massive concrete pillars, lined up with majestic precision, have earned it the nickname Underground Temple.

Harmonising ancient temple aesthetics with cutting-edge engineering, this extraordinary space garners high praise from domestic and international tourists, as well as disaster management professionals worldwide.
Metropolitan Area Outer Underground Discharge Channel Official Website

2. 7 Tour Routes Suitable

The facility offers seven distinct tour routes designed to showcase its role and underlying engineering prowess.
While guided commentaries are conducted in Japanese, joining a tour organised by a travel agency with an interpreter provides a deeper and more accessible understanding.

Underground Temple Course: Step into the Pressure-Adjusting Water Tank

This introductory 55-minute tour concentrates on the iconic Pressure-Adjusting Water Tank.
Following an insightful overview from the guide, visitors enjoy free time to explore the expansive space and photograph its 59 grand pillars at their own pace.

• Recommendation: Ideal for families, first-time visitors to Japan, and all age groups.
• Capacity: 50 participants
• Duration: Approx. 55 minutes
• Price: 1,200 JPY per person (tax included)

Shaft Experience Course: Exploring Shaft No. 1

This course includes access to the Pressure-Adjusting Water Tank as well as an exploration of the adjacent Shaft No. 1—a giant vertical pit measuring roughly 70 metres deep and 30 metres in diameter.
Participants walk along catwalk maintenance paths to experience its sheer vertical scale.

• Requirements: Safety harnesses and helmets are mandatory. Participants descend stairs inside the shaft, so those uncomfortable with heights should consider this in advance. Early booking is highly recommended.
• Capacity: 20 participants (limited places)
• Duration: Approx. 110 minutes
• Price: 3,500 JPY per person (tax included)

Pump Conquest Course & Pump Mastery Course

Pump Conquest Course

Introduced as an all-inclusive option, this popular course offers an in-depth look at the entire pumping and drainage process.
The tour begins in the exhibition room with an explanation of the facility's design and principles using Japanese visual panels.
Participants then move to the pump room to view four massive drainage pumps alongside their connected gas turbines and reduction gears—the true heart of the flood control system.

After learning about the backflow prevention valves that stop water returning from the Edo River, visitors are guided into the Underground Temple space to admire the pillars and examine the drainage impeller (runner) deep inside.

Note: Early booking is recommended. Please note that this tour cannot be conducted when the pumps are actively operating.
Capacity: 20 participants
Duration: Approx. 110 minutes
Price: 5,500 JPY per person (tax included)

Pump Mastery Course

A standard tour option designed to remain available even when the infrastructure is actively operating.

Similar to the Conquest Course, it begins with an informative overview in the exhibition room before proceeding to the pump room to inspect the vertical diagonal flow pumps and two-shaft gas turbines.

The tour concludes with scenic views from the catwalk overlooking the Pressure-Adjusting Water Tank and a dedicated vantage point overlooking Shaft No. 1.

Recommendation: Excellent for engineering enthusiasts, infrastructure fans, and group visits.
Duration: Approx. 110 minutes
Price: 5,500 JPY per person (tax included)

Impeller Exploration Course: Get Close to Massive Drainage Machinery

This popular route invites visitors into the deepest section of the Pressure-Adjusting Water Tank to inspect the massive drainage impeller up close while equipped with specialized gear.
Wearing hip chest-waders, safety boots, and helmets fitted with headlamps, participants wade through water up to 50 cm deep to experience the scale of the drainage machinery firsthand.

Requirements: Due to partially submerged sections, children under 130 cm in height cannot participate. Exceptionally popular among visitors interested in civil engineering.
Duration: Approx. 110 minutes
Price: 4,500 JPY per person (tax included)

Adventure Course: Walking Through Underground Tunnels

An advanced exploration route that encompasses both Shaft No. 1 and Shaft No. 3. Participants equip hip waders and helmets to walk through the actual underground river tunnels, gaining a heightened appreciation for disaster prevention engineering.
Upon completion, participants receive an official certificate naming them an Honorary Doctor of Ryukyu Disaster Prevention.

Recommendation: Though higher in price, this rare tour is exceptionally popular among specialist groups and international tour parties. Advanced booking is essential.
Availability: Seasonal only (November to May)
Duration: Approx. 240 minutes
Price: 15,000 JPY per person (tax included)

Minecraft Disaster Prevention Learning Course

A unique educational experience where the facility is recreated within the popular video game Minecraft.
Using Minecraft Bedrock Edition, participants virtually operate floodgates and experience facility functions before taking the physical tour, deepening their comprehension of flood defense.

Requirements: Participants are required to bring their own laptop or tablet with the software pre-tested. Rental PCs are also available for an additional fee.
Capacity: 20 players
Duration: Approx. 120 minutes
Price: 4,000 JPY per person (tax included)

River Basin Disaster Prevention Light-Up Course: A Nighttime Transformation

An evening event that combines the standard Underground Temple tour with dynamic light and sound displays.
The subterranean space is illuminated through four atmospheric scenes: Impending Heavy Rain, Occurrence of Flood, Discharge Channel Operation, and Clearing Skies, encouraging reflection on disaster readiness in an enchanting setting.

Price: 1,500 JPY per person (tax included)
Duration: Evening schedule

3. How to Book a Tour: Reservation Steps for Individuals and Groups

All tours for both individuals and groups require advance reservations, which can be made online via the official website or over the telephone.

1. Visit the Tour Schedule section on the official website.
2. Select your preferred date, time, and tour course.
3. Complete the required fields in the reservation form.

Important Guidelines

• Tours may be cancelled at short notice during active facility operation or scheduled maintenance. Always verify operational status on the official website before traveling.
• Pre-school children (under school age) are not permitted to join the tours.
• Children in junior high school or younger must be accompanied by an adult (a general ratio of up to 5 children per adult guide is recommended).

4. Future Plans and Disaster Prevention Tourism

As part of the Ministry of Land, Infrastructure, Transport and Tourism's Disaster Prevention Tourism initiative, the Metropolitan Area Outer Underground Discharge Channel continues to expand its tour options and raise international awareness regarding disaster preparedness.
Newly introduced routes, such as the Pump Conquest Course and the River Basin Disaster Prevention Light-Up Course, serve as engaging, hands-on content easily accessible to international tourists, establishing a new benchmark in educational tourism.
Beyond acting as functional infrastructure, the site functions as an educational facility that encourages visitors to consider disaster risks personally, regularly hosting schools and international delegations.
Given its convenient access from central Tokyo and diverse array of tours, the facility is poised to become a key hub for disaster prevention tourism in Asia.

5. Summary

The Metropolitan Area Outer Underground Discharge Channel offers an inspiring opportunity to experience Japanese flood management engineering and subterranean architecture firsthand.
For international travelers seeking unique infrastructure destinations, visiting this impressive facility makes an unforgettable day trip from Tokyo or Saitama. With an advance booking and translation arrangements in place, it promises to be one of the highlights of your trip to Japan.

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