The longtail-boat ride on the Mekong is alone a worthy day trip. This stretch of river is lovely -- and from the base of the cave entrance, you get a view of the high cliffs and swirling water of the Nam Ou River as it joins the Mekong. Inside the caves is enshrined a pantheon of Buddhist statuary. A day tour costs $5 per person in a boat shared by many tourists (more for a private charter). Arrangements can be made at any hotel front desk at an inflated rate, or you can just go down along the Mekong and negotiate with boat drivers directly (these guys are sure to find you). The half-day trip often includes a visit to a weaving village or the Lao Whiskey village, where you'll have a chance to try some really potent local brew.