This is a traverse of the dramatic massif of the Fforest Fawr (‘The Great Forest’, with ‘Forest’ here denoting a former Royal Hunting Ground, rather than an area full of trees), one of the least frequented parts of the Brecon Beacons National Park, linking the Black Mountain to the west with the Central Brecon Beacons to the east.
From the Craig y Nos Country Park, an idyllic spot on the banks of the Afon Tawe (River Tawe) with its Victorian Gothic building, the route follows the Tawe Valley for a short stretch to rise steeply up a hillside to the Penwyllt Quarry, from where you follow old tramways up through the limestone terrain of the Ogon Ffynnon Ddu National Nature Reserve, a large area of shakeholes and caves. You rise further along a good track and then trackless on up the slopes of Fan Gyhirych to its summit, the highest point of the walk, from where you have stupendous views of the surrounding upland moorland, the giants of the Beacons, the Black Mountain and of the Tawe Valley.
Follow a steep glacial escarpment above the Senni Valley down to a saddle and ascend Fan Nedd and then Fan Dringarth, from where the route turns to another dramatic glacial bowl in the Craig Cerrig-Gleisiad a Fan Frynych National Nature Reserve for a descent to the A 470.
An alternative finish at the Storey Arms Centre bus stop follows the Craig Cerrig-Gleisiad in a southerly direction and then the Craig y Fro escarpment high above the A 470.