Occupying a 90-sq-km site, there are around 35 caves located in dense primary rainforest close to the town of Lastoursville. They were formed some 50 million years ago, and human activity has been shown to date back some 7000 years when the caves were used in rituals. They are on the Tentative List for UNESCO World Heritage Status. Guides can be found in Lastoursville: ask at the Hotel Ngoombi. Be sure to wear suitable boots and take a waterproof torch.