Viengxay caves, Show cave system in Hūaphan, Laos.

The Viengxay Caves are a network of 480 caves in limestone mountains in Houaphanh Province, northeastern Laos. During the Second Indochina War the Pathet Lao used them as shelters from American bombardment; up to 23,000 people lived inside, and the caves held a hospital, a school, Pathet Lao offices, bakeries, shops and a theatre.

The cave system became a refuge during the 1960s and 1970s, sheltering tens of thousands of people fleeing aerial bombardment. It evolved into an underground base that supported military operations and civilian needs throughout the conflict.

The caves reveal how people organized daily life underground during wartime, with spaces for learning, healing, and work still visible today. Walking through them shows the determination of those who sheltered here and built a functioning community beneath the rock.

The caves lie about an hour by road from Sam Neua, near the Vietnamese border. Paths inside are uneven, with steep stairs and some slippery sections, so wear sturdy shoes. Signage and interpretation have been improved with help from the Caves Office, the UNWTO, the Netherlands Development Agency and the Asian Development Bank.

The caves once housed bakeries and shops where people bought daily necessities, creating a functioning underground town rather than just a military shelter. This level of organization reveals how the community sustained itself during extended periods underground.