The Digital Press

Tokyo has built the world’s largest underground flood diversion facility to protect the city from heavy rain and typhoon flooding, now open for public tours. This massive engineering feat channels excess water safely away, preventing urban flooding.

Why it matters: It protects Tokyo’s low-lying areas from flooding during extreme weather, safeguarding millions of residents and infrastructure.

The big picture: The 6.3 km tunnel system includes five giant shafts, each large enough to house the Statue of Liberty, showcasing advanced disaster-prevention engineering.

Quick takeaway: Tours are available but require advance booking, safety gear, and a Japanese-speaking guide due to restricted and carefully managed access.

Commenters say: Visitors are impressed by the scale and engineering, recommend bringing a translator, and note the tours’ popularity and some recent restrictions on movement inside.