This is a demanding but rewarding walk through the stunning Graig Cerrig National Nature reserve. We will follow the river then ascend to the top of Fan Frynach (a steep and slippery path). From there we follow a ridge through open moorland which is uneven and wet, but the views are spectacular (hopefully) !! We then descend onto the Roman road Sarn Helen through some lovely countryside. We will explore the stunning Blaen-Cwm-du before leaving the reserve. The track is wet, uneven, and slippery but well worth the effort. We will then climb very steeply onto Craig-Cwm-du hopefully taking in some excellent views as we cross more wet uneven moorland. After this we will descend through the reserve back to the layby. As described above the walk is not long but the terrain is quite challenging, we will take it slowly and enjoy this quiet corner of Bannau Brycheiniog together.