During the wars in Vietnam, an elaborate tunnel system was built over some 30 year period which began during the French occupation of Vietnam and continued till the Vietnam war. These tunnels were ridiculously narrow, stuffy, and I could not believe people practically lived in these tunnels.

Our tour guide demonstrated how to find an entrance to the Co Chi tunnel maze. He stood on a pile of leaf litter and challenged us to find the small entrance to the tunnels. No one figured it out until he took a stick and poked around on the ground. Surely, it was the sound made by the stick that gave away the location of the secret entrance.