The Vieng Xai caves are an extensive network of caves that served as hidden city during the Vietnam War. The area was home to the Communist army, who were fighting the royalist forces based in Vientiane and was bombed by the US army. Up to 23,000 people lived in the caves, which contained a hospital, military barracks, bakeries, shops, and even a theater. The Lao government hopes to promote the caves as a tourism destination, similar to the Củ Chi tunnels in Vietnam.