Matsushiro Underground Imperial Headquarters

The Matsushiro Underground Imperial Headquarters (松代大本営, Matsushiro Daihon'ei; "Matsushiro Imperial Headquarters Site") was a large underground bunker complex built during the Second World War in the town of Matsushiro, which is now a suburb of Nagano, Japan. The facility was constructed so that the central organs of the government of the Empire of Japan could be transferred there in the event of an Allied invasion.

Source: Wikipedia — Matsushiro Underground Imperial Headquarters (CC BY-SA 4.0)