Cu Chi Tunnels are a vast network of underground tunnels from the 1940s, expanded by guerrilla Viet Cong during the American War. The tunnels were hiding places, as well as communication and supply routes, hospitals and living quarters. Sections of the tunnel system large enough for a 40kg person have been widened to cater for larger bodies, but it's still a tight fit. Cu Chi is a short drive from HCMC and most Saigon tour companies offer day trips.
When in HCMC take a tour of the Cu Chi Tunnels, easy accessible by road or boat up the Saigon River. As the Viet Cong's base of operations for the Tet Offensive in 1968, the Cu Chi Tunnels played a chief role in the Vietnamese winning the American War. The tunnels frustrated the Americans by drawing out the war and extending U.S. fatalities and costs until the United States finally withdrew in 1972 and the Republic of Vietnam fell in 1975.