The tunnels open to tourists are just a tiny fraction of the Cu Chi network at its peak; most of the tunnels have collapsed from disuse, so the tourist site features one enlarged tunnel and a few bolt-holes for demonstration purposes.

The bolt-hole shown above demonstrates the tunnels' small size and high stealth factor. The holes and tunnels fit the slim, compact frame of most Vietnamese, and exclude the tall, stocky frames common among American servicemen.

A Cu Chi guide demonstrates how to enter and shut the hole - the guide enters feet first, holds the lid high above his head (left), and bends at the knee so the rest of his body can slide into the opening (center).

Once his whole body is inside, the guide then slides the lid into place (right), leaving almost nothing on the surface that indicates the location of the hole.

For American servicemen in the area during the Vietnam War, it must have felt like being attacked by ghosts.