(S) From YHA Brecon Beacons (formerly YHA Llwyn-y-celyn) take the path out at the back (sign-posted Woodland Path and Reading Circle) down to the Afon Tarell, crossing over near a waterfall and climb up the other side to join the Taff Trail. Turn right and head south along the well marked trail to reach Storey Arms Centre (Canolfan y Bannau).
(1) Ignore the path going left next to the red telephone box, rather keep straight on by the side of the road as it bends to the right. Fortunately, there is a path, through a wooden gate, that runs parallel with the A 470 by the side of a Forestry Commission pine plantation. Keep on this track until you reach the Pont ar Daf car park and the start of the Pen y Fan walk. Take the path through the trees to a wooden gate and the bridge that crosses the Taf Fawr. The trail is easy to follow as this is one of the most popular walks in South Wales and there will almost certainly be other people walking the same route. The path climbs steadily but not acutely, so progress should be easy and without much difficulty. At the crossing of paths at Bwlch Duwynt, head straight on upwards north-east to reach Corn Du.
(2) The path turns right and hugs the crags with great views down to the left of the lake Llyn Cwm Llwch and the headwaters of Nant Cwm Llwch. After a short distance, the route reaches the cairn on Pen y Fan (886m). If there are not too many people up there with you, take time to contemplate the view. If not, head off the summit south-east along Craig Cwm Sere, looking down to the left along the valley of Nant Sere. Ignore the path leading off to the left that goes to Cribyn, unless you want the extra climb as there is a path that comes back to meet the trail at Bwlch ar y Fan.
(3) From the crossing of paths head east up the slopes of Fan y Big. Ignore the first path off to the right but continue until you reach another T-junction of paths and the famous "Diving Board" - a slab of rock that juts out on which you can stand (if you dare). Turn south along Craig Cwmoergwm as it rounds the headwaters of Nant Menasgin until you reach a signpost indicating footpath south-east to a pile of stones and on to Craig y Fan Ddu. At the pile of stones, the path turns north-east to the edge of the escarpment to a waterfall that plunges over the edge, called Blaen Caerfanell Waterfall.
(4) Turn away from the waterfall to head south-east again along the crags, finally descending to Nant Bwrefwr at the edge of a pine forest and a series of waterfalls. The path meets a shale track along a wooden fence at a cattle-grid. The Blaen y glyn car park is on the left with a nice wooden table and bench on the right just after the entrance (there's also a metal kissing gate). However, the route goes right along the track to meet a minor road after about 50m. Go straight across this road to follow the path through the pine forest. This forest track (also cycle track Nº 8) crosses a number of streams but is otherwise devoid of interest apart from the occasional glimpse of the Nant Bwrefwr valley. When a path comes in from the left and crosses the track to head up to the right, follow it through the trees to Pen Rhiw-calch. Keep heading north-east along the top edge of the forest past Bryn-melyn Farm with some stunning views down to the left of Talybont Reservoir. A dry stone wall comes in from the right and leads to a junction of tracks where a footpath sign indicates the route to the right. Go through the wooden five-bar gate towards Bwlch-y-waun farm, heading east over the fields and down to a minor road through a metal gate. Turn left up to the road to reach Pen-y-bailey.
(5) Turn right here to head down past Pen-y-beili Farm and Llwyn-yr-êos Farm to get close to the Afon Crawnon near a waterfall. The path bears left heading for a small wood to find a footbridge over the Monmouthshire and Brecon Canal. Turn left along the towpath, under the road and follow the canal for a few miles past locks and over footbridges along the Usk Valley Walk. Before reaching Llanddetty Hall the path reaches a bridge over the canal (still on the Usk Valley Walk) at the edge of a pine forest. A track leads right to the main B4558 road and a small church but the route crosses the canal and heads north-west then west to meet a minor road at a cattle-grid. A sign-post clearly indicates the route going left across the fields down to another track crossing. Bear left over a stream then down to the right and into the woods before cutting back on the right to cross the stream again and come out of the woods to see the Talybont Reservoir Dam down to the left. Head straight for YHA Brecon Beacons Danywenallt crossing over the disused railway.(E)