Serene and unpretentious, Thakhek lies across the Mekong River from the Thai town of Nakhon Phakom. The main draw card in the area is the spectacular Konglor Cave, located in the Phou Hin Bun National Biodiversity Conservation Area. This vast cavern system snakes for almost 8km through the limestone mountains, reaching up to 50m in height at some points, and encompassing a dazzling array of stalactites and stalagmites along the way. Konglor is accessible by way of boat tours along the Hin Bun River, which runs through the length of the cave. The surrounding national park is a worthy attraction in its own right, blanketed with ancient rainforests and dotted with impressive karst formations and glittering lakes.