Structure of Cu chi Tunnels System: In terms of scale, the tunnel system has a total length of over 200 km, with 3 different depth layers, the upper layer is about 3 m deep under ground, the middle layer is about 6 m deep under the ground, the bottom layer is deeper than 12 m. At this time, the tunnel is not only a shelter but has become a place to live, ambulance, meeting, …