The Matsushiro Underground Imperial Headquarters is one of Japan's more sobering wartime sites: a network of tunnels and chambers carved into Mount Zouzan near the former castle town of Matsushiro, about 13 kilometres south of central Nagano. The complex was intended as the final redoubt of the Japanese empire — a place from which the war would be directed, the Emperor sheltered, and NHK propaganda broadcast if the home islands were invaded. Roughly 10 kilometres of tunnels were dug, several chambers lined with concrete, and a dedicated imperial bunker completed before surrender ended construction.
Part of the tunnel network is now open to visitors at no charge. The preserved section runs about 500 metres and includes the prepared imperial chambers and the NHK broadcasting room. The rock walls still show the drill marks and blast scars of the original construction. The tunnels maintain a cool, damp temperature regardless of season. The site is managed locally and is low-key: no dramatic lighting or multimedia. An adjacent memorial acknowledges the Korean workers whose forced labour drove the construction. To reach Matsushiro, take the bus from Nagano Station (about 30 minutes); the tunnel entrance is a short walk from the Matsushiro bus stop.