Vieng Xay, located northeast of the provincial capital, boasts over 100 limestone caves, 10 of which have immense national and historical significance as the hidden headquarters of the former Pathet Lao from 1961-1975.
These limestone karst cave networks sheltered their headquarters during their struggle with the American-backed Royal Lao Government. In these caves the Pathet Lao established a “Hidden City” which supported around 20,000 people. During nine years of almost constant bombing, they sheltered in caves and surrounding jungle. Most of their daily lives were led under cover of darkness. Schools, hospitals and markets as well as government ministries, a radio station, a theatre and military barracks were all hidden in the caves.
See: Vieng Xay Caves – Life Underground