One of the most respected holy sites in Lao; Pak Ou Caves have a history dating back thousands of years. Packed with over 4,000 Buddha icons, the caves, a shrine to the river spirit and Lord Buddha, are set in a dramatic limestone cliff at the point where the Mekong joins the Nam Ou River. There are two caves to visit, the lower cave called Tham Ting and the upper cave Tham Theung, both boasting miniature Buddhist figures that are mostly made from wood.