Introduction to the air-raid shelter: The air-raid shelter is located halfway up Huangshan Mountain. It was built in the 1930s, with a total length of more than 200 meters. It has three entrances, hidden in the recesses of the mountain. The three passages are distributed in a "Y" shape, leading to Yunxiu Tower, Thatched pavilion and pine hall. It is equipped with a guard box, an emergency operation command room, a twin generator room, Chiang Kai-shek's office and living room, etc., and is equipped with ventilation facilities. It is the largest and best-preserved underground command center of the Anti-Japanese War currently open to the outside world in China.