Formerly called as “Lijhengjiao Underground Command Post,” also known as “Huxi Longmen Nankan Locked Position” and uniformly named as “Longmen Biso Battlefield” by Penghu County Government in 2020, the place is roughly divided into two areas: the outer area is a landscape architectural park that mainly includes stores and stalls, public toilets, tourist service center and parking lot, and the inner area is the Longmen Tunnel. The main structure of the tunnel was built during the Japanese colonial period and was one of the important military positions in Penghu long ago. Later, the Kuomintang troops came and took over the place. In 1980, the National Army Squad 168 under Penghu Defense Command (now disbanded) also built the machine gun forts, 57 anti-tank gun forts, underground command posts, radar stations, and other facilities which are the complete fields in the Longmen Tunnel opened now.
With a total length of 705 meters, a width of 60~80cm and a height of nearly 2 meters, the tunnel can accommodate 150 infantries. Gun forts and launch points were designed for armed forces to defend against enemies, and a radar station was set upon the underground command post (now abandoned and unused).
Ten machine gun forts (including a telephone operator room), two 57 anti-tank gun forts, one ammunition depot, one kitchen, one military simulation room, one cistern and fourteen guard units were built in the tunnel.