13-04-2025
A new tour of Tokyo's most underground attraction
Staring into a pitch-black void. Wading through knee-deep, stagnant water. Dangling a camera over a railing above a concrete abyss deep enough to comfortably fit the Space Shuttle, praying that you can grab a photo without losing your grip.
These are just some of the joys of touring the Metropolitan Area Outer Underground Discharge Channel, ostensibly a critical part of the capital region's defenses against severe weather events but perhaps the greater Tokyo's areas most unique tourist attraction.
From April 16, the facility will be conducting monthly tours of areas previously unavailable to the public: For ¥15,000, the new Underground River Walking Adventure Experience Course will bring visitors down to the bottom of the discharge channel's 70-meter-deep, 30-meter-diameter No 3. shaft, one of five concrete silos used to contain surging waters from the Kuramatsu, Naka and other small- to medium-size rivers that have flooded the surrounding region throughout history.
The new tour only briefly walks participants down one of the tunnels connecting the discharge channel's containtment silos and pressure-adjusting chamber. |
OWEN ZIEGLER
On a Mar. 26 demo tour, I had the chance to experience the newly accessible portion of this engineering marvel. The roughly four-hour tour starts from the RyuQkan, the facility's museum and control room, which is located a 30-minute walk from Minamisakurai Station in Kasukabe, Saitama Prefecture.
Next, it's a short bus ride to the No. 3 shaft. I start with a brief yet dizzying view from the top before descending 70 meters via elevator. Here, provided waders come in handy: Though Tokyo hasn't seen much rain prior to my tour, a few centimeters of water remain in this titanic cistern. My headlamp only brightens a meter or so in front of me, but the real attraction is how the absolute darkness of the tunnels on either side of the shaft swallows up any feeble attempt to illuminate them.
The view from the top of the 70-meter-tall No. 1 shaft is dizzyingly exhilirating. |
OWEN ZIEGLER
While the tour doesn't walk visitors beyond a few steps through these 6.3-kilometer-long tunnels connecting each silo, just being in the presence of such an unworldly, shadowy cavity feels as if I've entered a scene from a Junji Ito horror manga, my very own hole in Amigara Fault calling to me.
It's not all doom and gloom, though — also at the bottom of the No. 3 shaft is a population of small fish, crustaceans and other riverbed-dwelling creatures who get swept into the discharge channel whenever the rivers above surge to dangerous levels.
Walking through the pressure-adjusting chamber evokes memories of both the Lord of the Rings franchise and megalithic sites. |
OWEN ZIEGLER
From there, the Underground River Walking Adventure Experience Course proceeds to areas of the discharge channel already accessible via guided tour. There's a stroll along the catwalk near the top of the No. 1 shaft followed by a 117-step descent (beware the 117-step ascent) down to the pressure-adjusting water tank, a massive chamber designed to hold water from the containment shafts and ensure the collected surge water enters the Edo River, the exit point of the discharge channel, at a suitable rate.
After walking the length of this so-called 'underground cathedral' with its dozens and dozens of 18-meter-tall pillars — features that evoke equal parts Mines of Moria and prehistoric megaliths — the tour finishes with a stroll through standing water until just under a gas-turbine impeller capable of draining 50 cubic meters of water per second up and out of the pressure-adjusting chamber.
An impeller used to draw water up and out of the pressure-adjusting chamber and into the Edo River marks the end of the discharge channel's new tour. |
OWEN ZIEGLER
While ¥15,000 may seem like a steep price for a tour nowhere near as Instagrammable as a night out in one of Tokyo's nightlife districts, it will surely scratch the itch of anyone wondering what goes on beneath the surface of Japan's largest megacity.
The Underground River Walking Adventure Experience Course tour on April 16 has sold out. Bookings for the May 14 tour will open on April 14. Tours require a minimum of five participants and a maximum of 16 and are subject to cancellation depending on the weather. For more information and to make reservations, visit
