The tunnels are the reason to come to Cu Chi. The district has two visitor sites — Ben Dinh, closer to Ho Chi Minh City and better connected by tour buses, and Ben Duoc, further north and considerably more atmospheric. Both open sections of the original tunnel network to visitors, widened slightly to accommodate foreign-sized bodies. Both have documentary films and museums on site that explain the history of the tunnels and the American War with real force; don't skip these.
A half-day from Ho Chi Minh City is enough for either site. The underground sections are claustrophobic and warm — a constant 25–30°C — and most visitors are ready to resurface after an hour below. Above ground, the sites preserve bomb craters, tank traps, and demonstrations of Viet Cong camouflage techniques. A firing range at each site lets visitors fire period weapons for a fee; it is entirely optional and easy to skip.