The Kashima Naval Air Group was formed in December 1938 as an Imperial Navy training unit for seaplane crews, with its base laid out along a lakeshore. As the Pacific War turned against Japan, training gave way to homeland air defense, and in the war’s final months the unit formed special attack squadrons that flew toward Okinawa. The base stopped with the war in 1945, and much of it simply froze in place.

What survives is remarkable: the concrete headquarters building, the boiler house with what is said to be Japan’s oldest surviving coal-fired heating boiler, the generator building and the garages, all weathered but standing. I featured it as #57 in my book Nippon No Haikyo back when it was still a locked-away ruin. Since 2023, part of the grounds has been cleaned up and opened to the public as a memorial park, making this one haikyo you can now visit legally.