Members of Japanese Navy Corps Engineers, Yamane Division dug a tunnel complex for the Navy’s Okinawa headquarters bunker in 1944. The semi-circular tunnels hardened by post and concrete were 450 meter in length at that time. They served as underground headquarters to endure the American bombardment and long drawn out fighting and could sustain 4000 soldiers. After the war, tunnel remained untouched for many years. The remains of those who died were collected and a 300meter portion centered on the commander’s office was renovated and opened to the public in March 1970 by the Tourism Development Board.