Libmanan is an extremely large municipality, one of the biggest in Camarines Sur. It stretched across nearly the whole width of the Bicol peninsula, from where it borders Cabusao Municipality on the San Miguel Bay all the way out to the Ragay Gulf, including three islands known locally as the 'tres Marias', including one island known as 'puro island'. The main town, or 'poblacion', is located along the Libmanan River on the lowland alluvial plain adjacent to Cabusao.
Heading to the southern coast from the poblacion the municipality becomes hilly. In this hilly region between the poblacion and the highway lies the Libmanan Caves National Park. Continuing on towards the coast from the hills, the municipality becomes truly mountainous beginning in Barangay Malinao beyond the Pan-Philippine Highway, where the "Boro-Boro Spring Resort" is located; a series of waterfalls that are a locally popular swimming destination. Beyond Malinao the upland region features the mountain 'Tancong Vaca' - in the local dialect meaning 'the cow's hump' - which is a local landmark visible from most locations on the Pan-Philippine Highway in western Camarines Sur and was a base of operations for local guerrillas fighting the Japanese during World War II.
The municipality's rural barangays lie behind Mount Tancong Vaca, and mostly lack access to paved roads, of which there is only one which terminates in the fishing village of Barangay Bahao, within sight of the tres Marias.
