The woodland of Cwm Clydach grows on steep slopes alongside a deep river gorge. It is the largest and most representative area of native beechwood in South East Wales.

The river has cut deep into the valley forming steep cliffs, and spectacular waterfalls. The air is humid close to thefast moving river, and many species of moss can be found growing here. Clinging precariously to the cliffs are yew and whitebeam trees. Ground plants are relatively sparse, especially in the shade under the beech trees. A good variety of woodland birds can be seen.