The underground cathedral protecting Tokyo from floods (2018)

The underground cathedral protecting Tokyo from floods (2018)
bbc.com

It is limited viewing, requires a reservation & the slots run out practically in seconds. Tough for us residents to get it as well. My wife could snag it in her third try, as a late birthday trip last year.

It is gargantuan & having massive holding capacity. To give semblance with something familiar, it was like standing in NY Grand Central station, except it was felt bigger, empty, damp & illuminated by floodlights from all sides. It is probably one and half football fields in length & scales high as much as a five storied building. Uploaded three pics to show the scale of this megalith. (The base of the pillars here are taller than average height of person to give a rough scale. The stairs come down from the ground level)

https://i.imgur.com/Jtcy0Ct.jpeg https://i.imgur.com/8Q08eKS.jpeg https://i.imgur.com/y75sfGP.jpeg

In addition to this underground chamber, there are two massive pumps on either sides, which divert the water from whichever river is surging to the other (Arakawa & Edogawa possibly). The chamber is the buffer zone between the rivers, not a storage tank ultimately. I was told by the civil engineer of this plant they could pump out as much as a jumbo jet's volume per minute in its storm surge channel/drain to manage flooding. You can walk up to the turbine room at the end of this room, and see its massive blades at an arm length. All with earthquake protection in place as well. Honestly mind-blowing piece of engineering.