Situated on the Chaillu Massif, this park is known as a Pleistocene refuge, meaning that its ancient savannahs, forest and the caves date back at least 40,000 years. It is important to protect the river basins here, as well as the wide diversity of plants and apes. One ape in particular, the sun-tailed monkey, was first discovered here in 1984. Permits are available from the from ANPN office in Mbigou, but there is as yet no infrastructure for visitors.
Access by road from Mbigou or Pana (you'll need a 4WD); alternatively, take the train to Lastoursville and then travel by minibus or clando to Popa.