What trip to Vietnam would be complete without a trip to visit the famous Cu Chi Tunnels? From Wikipedia:

The tunnels of C? Chi are an immense network of connecting underground tunnels located in the C? Chi district of Ho Chi Minh City (Saigon), Vietnam, and are part of a much larger network of tunnels that underlie much of the country. The C? Chi tunnels were the location of several military campaigns during the Vietnam War, and were the Viet Cong’s base of operations for the T?t Offensive in 1968.
The tunnels were used by Viet Cong soldiers as hiding spots during combat, as well as serving as communication and supply routes, hospitals, food and weapon caches and living quarters for numerous North Vietnamese fighters. The tunnel systems were of great importance to the Viet Cong in their resistance to American forces, and helped achieve ultimate military success.

I went with a few friends, and took the standard tour. Luckily, I brought my headlamp – always comes in handy.