The Cu Chi caves outside Saigon, coupled with booby traps sprinkled around, were used by the Viet Cong during the war to hide from and surprise U.S. forces. The cheapest way to get to the caves was to join a group tour, which we did, but was somewhat intolerable due to the tour guide having an extremely thick accent to the point that we couldn't understand most of what he was saying. It was, however, interesting to learn how the caves were made. Each family was responsible for one hole and each hole was 10 meters away from the next. The father in each family did the digging while his wife and kids sharpened bamboo for the booby traps. When the hole was several meters deep, the men dug sideways to connect their holes together and then covered the original openings above. After that was complete, the repeated the process to create multiple layers of tunnels. We got to go down inside one of the tunnels and it was a bit claustrophobic, but it could have been worse. I have a feeling that the tunnel that tourists are allowed to go into was a bit wider than many of the ones used during the war.
As with Phnom Penh, Saigon isn't a bad city, but there isn't all that much to do, so we're moving on.