upper reaches are steep and good walking fitness is essential. Interesting features include a nature reserve, the mountain geology and excellent views of all the high peaks and the valleys associated with them.
From the car parking area at Pont y Caniedydd turn south-east, cross over the bridge and up the lane ahead. On the right of the road into the valley of Cwm Sere is a woodland nature reserve managed by the Brecknock Wildlife Trust (see Walk 7).
Nant Sere drains the vast cauldron formed by the headwalls of Cribyn and Pen y Fan. Water avens and mossy saxifrage grow on the banks of this mountain stream which then flows on through ash, alder and birch woodland. Cwm Sere is extremely rich in flora and fauna with over 200 species of flowering plants and ferns, abundant fungi, birds and insects, at least two of which are rare arctic-alpine species.
Continue past the turning on the left to Bailea Farm, and follow the road up the hill to where it swings sharp left and through a gate. Ignore this turning and follow the stony track, the old Roman Road (see Walk 11), for 250m straight ahead to a gate in the hill fence, on the far side of which is a National Trust sign for Cwm Cynwyn.
On the left is the ridge of Cefn Cyff which leads down from Fan y Big and straight ahead is the ridge of Bryn Teg which you are about to ascend to the summit of Cribyn. On the right is Cefn Cwm Llwch which leads down from Pen y Fan and this will be your descent route.
Continuing from this point at the hill fence, ignore the stony track which goes off to the left and head straight for the ridge ahead of you. After a concentrated pull up the beginning of this ridge you arrive at a cairn. The ridge ascends in three main steps and after the second major climb you arrive at a level section marked by a second cairn. The final step is the ascent of the prow of Cribyn. The alternative route to Pen y Fan leaves from here.
Pen y Fan from Bryn Teg
The step in the middle of the ridge has formed due to the underlying geology. This step is known as a secondary scarp and results from a change from Brownstones to Senni Beds.
Climb the narrow path to the summit of Cribyn, then descend west along a distinct eroded path to the col. To the south is the Neuadd Valley where two small reservoirs dam the Blaen Taf Fechan, which is fed by surface run-off and ground-water collected in this basin.
From the col, climb steadily (W) following the line of Craig Cwm Sere to the summit of Pen y Fan. The final ascent to the summit of Pen y Fan is up a very stony area and The National Trust has built a zigzag path up this face to the top.
Walk across the flat surface of Pen y Fan, which is also badly eroded, to the trig point. This can be found in bad visibility by carefully following the north-east crag line. The trig point is at the end of this to the left. The north-east face is very steep and care must be taken not to stray too near the edge, especially in strong south-westerly winds or when corniced in winter.
Leave the summit of Pen y Fan by carefully scrambling (NNE) down the exposed Plateau Beds. The rocks can be slippery but the route drops quickly to the fine ridge of Cefn Cwm Llwch.
Follow the path along the flat section of the ridge, leaving it when it drops gradually to the valley of Cwm Gwdi. Keep to the eastern edge of the ridge, following a path through some boggy areas with mainly heather, past the disused quarries and onwards to Allt Ddu.
From the pools on the summit of Allt Ddu drop down past the stones of the quarry towards the Plas-y-gaer settlement. Just on the edge of this hill there is a distinctive furrow in the hillside which is an old quarry path. Continue down this path (marked with a dotted line on the map) towards the settlement, descending the front of the ridge. The descent of this ridge provides a good view of the settlement with the earth bank being now planted with a line of large trees.
Blaen Taf Fechan and the Upper Neaudd Reservoir
At the bottom of the slope turn left in front of the settlement. As you come round the corner of the settlement follow the path diagonally down to the left, arriving at a stone wall. There is a finger post and gate. A track leads to the farm (Plas-y-gaer). At the farm turn left through a gate and right into a field at the blue waymark post.
From here head across the field to a line of pylons reached through a gap in the trees. Turn right at a line of trees and walk up to a gate and stile in the right corner of the field. After crossing the stile, descend a shallow valley to another stile which you will see in the field about 60m in front of you. Follow the wire fence on the right-hand side downslope to the derelict buildings. Walk to the left of the farm buildings to a stile in a fence and onto a track. At the end of the farm track is a gate beyond which is a tarmac road. Turn right on the road and down the hill to the start at Pont y Caniedydd.
Alternative route
Follow the Cribyn face path off to your right leading to the col between Cribyn and Pen y Fan.
The further you travel, the steeper the cliff becomes with the Brownstones becoming more prominent up to your left. These are responsible for forming the red soil of the path. On a still day you will often hear the sound of croaking ravens high above you.
Towards the end of the path, as you cross a number of small gullies, there are quite steep drops away to the right and the path surface becomes uneven and stepped. As you are walking along this path the views of the main face of Pen y Fan change and become even more impressive (see ‘Geology and geomorphology of Pen y Fan,’ Walk 5). This path can be dangerous in winter conditions and crampons and ice axe may be needed.
FLORA OF NORTH-WEST FACE OF CRIBYN
Ledges of this face are more accessible to sheep grazing than those of the north-east face of Pen y Fan and so the interesting arctic-alpine plants are not so prolific. Nevertheless, roseroot (Sedum rosea), mossy saxifrage (Saxifraga hypnoides), purple saxifrage (Saxifraga oppositifolia), and vernal sandwort (Minuartia verna) are common. Rock stonecrop (Sedum forsteranum) can be found but is more localised. Other species include cowberry (Vaccinium vitis-idaea), green spleenwort (Asplenium viride), brittle bladder-fern (Cystopteris fragilis), limestone bedstraw (Galium sterneri), viviparous fescue (Festuca vivipara), great wood-rush (Luzula sylvatica), cowslip (Primula veris), common wild thyme (Thymus drucei) and northern bedstraw (Galium boreale). The wet ledges also support an excellent collection of upland bryophytes.
WALK 7
Cwm Sere Valley
| Start | Pont y Caniedydd (SO 039 244) |
| Distance | 6.25km (3.6 miles) |
| Total Ascent | 250m (820ft) |
| Map | OL12 Western Area |
A low-level walk around one of the most beautiful and spectacular of the Welsh valleys. The sheer size and steepness of the impressive north-east face of Pen y Fan can be fully appreciated from the head of Cwm Sere. Like all valley walks there is little danger of getting lost, even in poor weather, and it can be enjoyed with a leisurely approach requiring not too much exertion. The main features of interest are the geological features of the headwalls and north-eastern
