Plynlimon, or Pumlumon in Welsh (also historically anglicised as Plinlimon, Plynlymmon or Plinlimmon), is the highest point of the Cambrian Mountains in Wales (taking a restricted definition of the Cambrian Mountains, excluding Snowdonia, the Berwyns and the Brecon Beacons), and the highest point in Mid Wales.

The highest point of the massif itself is Pen Pumlumon Fawr, which is 752 metres (2,467 ft) above ordnance datum.

This watershed area has been affected by loss of biodiversity, erosion of the peaty soils' structure, and accelerated drainage.

The principal land cover within the project area is dominated by a complex mosaic of locally, nationally and internationally important habitats and species, such as dry and wet dwarf-shrub heathland, blanket bog, unimproved acid grassland and a number of oligotrophic lakes.

Agriculturally improved grassland, broadleaved woodlands and forestry plantation are also characteristic features of the area.