Carboniferous limestone outcrops along the south fringe of the Borough, and also in the far north (although almost totally inside the Brecon Beacons National Park) and support distinctive calcareous woodland. The most clearly influenced woods are those occurring in old limestone quarries where amongst ash and oak trees and hazel coppice, field maple, dogwood, spindle and even wayfaring tree form understories.  These woods also have exceptionally species-rich ground flora, which amongst the bluebell, wood anemone, primroses and ramsons include early dog’s-violet, toothwort, common-spotted orchid, twayblade and moschatel, and even the occasional early purple orchids and, stands of herb Paris.