As explosion the sise of a nuclear bomb once went off there. The area was owned by the Japanese Red Army. Someone noteworthy wrote a book on it. Couda been the Thunderbolt Kid or the Krakauer fella.
Bill Bryson wrote about it in one of his books, but there's a lot more around about it.
Doomsday cult Aum Shinrikyo tested sarin gas at Banjawarn station before Tokyo subway attack