Japan has a justly bad reputation for over-engineering its rivers - but sometimes the results are spectacular, like this underground concrete cathedral used for storing floodwater. It's a spectacular photo opportunity but you would never know was there, under rice paddies in the outskirts of Tokyo.
Bring good shoes and a Japanese-speaker for the tour.
720 Kamikanasaki, Kasukabe city, Saitama 344-0111
Google map: tinyurl.com/3263c35
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