The Cu Chi Tunnels are 75 miles of interconnecting tunnels that were used by the Vietnamese navy in the Vietnamese War (or American War as they call it). They served as hiding spots and as routes for communication and provides. Lots of troopers even lived in these tunnels for intervals https://sai-gon-list50482.p2blogs.com/27579736/the-2-minute-rule-for-sai-gon