On our way down to Hue, we made one brief, but solid stop at the Vinh Moc Tunnels. From Wikipedia:
Vinh Moc (V?nh M?c) is a tunnel complex in Quang Tri, Vietnam. During the Vietnam War it was strategically located on the border of North Vietnam and South Vietnam. The tunnels were built to shelter people from the intense bombing of Son Trung and Son Ha communes in Vinh Linh county of Quang Tri Province in the Vietnamese Demilitarized Zone. The American forces believed the villagers of Vinh Moc were supplying food and armaments to the North Vietnamese garrison on the island of Con Co which was in turn hindering the American bombers on their way to bomb Hanoi. The idea was to force the villagers of Vinh Moc to leave the area but as is typical in Vietnam there was nowhere else to go. The villagers initially dug the tunnels to move their village 10 metres underground but the American forces designed bombs that burrowed down 10 metres. Eventually against these odds, the villagers moved the village to a depth of 30 metres. It was constructed in several stages beginning in 1966 and used until early 1972. The complex grew to include wells, kitchens, rooms for each family and spaces for healthcare. Around 60 families lived in the tunnels; as many as 17 children were born inside the tunnels.