We got on a bus from Phong Nha village to Huế which would stop a couple of times along the way in the Demilitarised Zone (DMZ) in central Vietnam, the area that was used as the border and separation between North and South during the American / Vietnam War. The first stop was at the Vinh Moc Tunnels, this was a village in the DMZ that was famous for building a network of tunnels, in three stages to take the entire village underground away from the bombing by the USA.
This full network of tunnels housed areas for sleeping, eating, working, even a maternity area. The tunnels were a few KM long in total and went down to depths of 23m at the deepest. We walked through the tunnels and came out through one of the exits straight on to a beach on the South China Sea. There was also a small museum here to show all of the tunnels in the region that were built during this time, of which there were dozens.