a small path which leaves the main track and bears left (N) towards the pile of stones at the disused quarry of Cwar Mawr (SN018 236). From here descend west-north-west (292°) to the spur of Twyn y Dyfnant and down the steep slope to the hill fence, keeping to the right of the coniferous forestry.
Cross the fence through a gate (SN009 241) and follow the line of trees diagonally down the slope to the right. At the end of the tree line turn sharp left and drop down to the field below. An indistinct path leads directly down the field after 80m. Head for the junction of hedges to the left and continue down the slope to the ford across the stream (SN007 244) and back to the start of the walk.
CORN DU
Corn Du is the site of a Bronze Age cairn, and the stones near the edge are the remains of an excavated funerary mound (also see ‘Cairn Pica,’ Walk 17). Corn Du is a fine vantage point with views to the west of the Fans and, in particular, of the finely sculpted headwall of Fan Fawr to the south-west. In the valley just below to the west is Blaen Taff Fawr, the headwaters of the River Taff. The south-east presents a quite different aspect down into the valley of Neuadd with its reservoirs and continuing view towards the South Wales coast in the distance.
WALK 3
Cwm Llwch Valley
| Start | Llwynbedw, Cwm Llwch (SO 006 246) |
| Distance | 6km (3.75 miles) |
| Total Ascent | 340m (1115ft) |
| Map | OL12 Western Area |
Cwm Llwch is a beautiful valley leading from the wooded plain south of Brecon and up into the U-shaped glacial upper reaches, climbing under the spectacular head wall of Corn Du. This walk is one for a more gentle frame of mind or perhaps when conditions suggest caution in venturing too high on the mountains. No great height is reached but the atmosphere of the Beacons is savoured and the scenery is typical of the northern valleys. An early start is rewarded by the eastern sun lighting not only the valley floor and waterfalls, but also the north-eastern face of Corn Du. The walk is safe in terms of route finding and requires average fitness. Features of interest include the geology and glaciology, the plant and birdlife, waterfalls, mountain scenery and local mythology.
Start at the end of the car park where there is a ‘NO MOTORS’ sign. The ford and the hillside on the left of the car park is your descent. Follow the track leading into the valley, coming soon to another ford across the same stream, Nant Cwm Llwch, with a wooden bridge on the left, through a second gate and then between wooded banks with fields on either side. From here there are good views into Cwm Llwch, with waterfalls in the foreground and a backdrop dominated by Corn Du straight ahead and Pen y Fan on the left.
GEOLOGY AND GEOMORPHOLOGY OF CWM LLWCH
Cwm Llwch was carved by glaciers during the last ice ages but its shape is different from many of the other glacial valleys in the Beacons. The upper section is relatively flat and contains a corrie lake, Llyn Cwm Llwch, but the gradient steepens in the middle section where the waterfalls are found, before the gradient eases again near Cwm-llwch Cottage. The reason for this may be a more resistant band of rock which is also responsible for the formation of the waterfalls. The classical U shape of glacial valleys has been further modified in the middle section by two streams which have cut down into the valley floor, leaving a ridge which the main footpath follows.
The track continues southwards between old stone walls and then detours around Cwm-llwch Cottage. Leave the cottage on your left and skirt around the right of the farmyard by crossing over two stiles. The wide open track ahead takes a direct line up a spur of land with stream courses on either side. However, this line is of little interest and avoids the superb waterfalls glimpsed earlier. Descend instead to the left and walk along the fence which soon reaches the stream. Here a small track crosses to the left bank although either can be followed to the waterfalls.
The hill fence crosses the stream ahead but there is a low-level stride over it just before the stream divides. The left branch of the stream is the more interesting and just ahead is an impressive waterfall. This can be climbed on the right arriving first at a small pool above the lower fall.
Climb up the right side of the upper fall or more easily up the hill on the right of the lower fall, reaching a series of smaller waterfalls from where there are magnificent views of Corn Du. When the stream starts to break up into many smaller tributaries, leave the stream to the right, striking westwards to the corrie lake of Llyn Cwm Llwch.
Llyn Cwm Llwch had an enchanted island only accessible through a tunnel from the shore. The island rose out of the water only on May Day when fairy flowers could be gathered to fairy music. The flowers were so lovely that a sacrilegious visitor brought some away with him and down the mountain. When they faded, the island disappeared below the waters and has never been seen again.
Cwm Llwch, Corn Du and Pen y Fan
From the northern end of the lake the path heads down the valley on the return walk. Descend to a cairn where the track is joined by the one from Corn Du which zigzags down from above the lake. Continue down on the crest of a spur which divides the valley into two in its upper reaches, gaining a good view of the northern end of Cwm Llwch and the agricultural areas to the north.
On reaching the hill fence, cross it by a stile alongside which is a National Trust sign for the Brecon Beacons. This is where the ascent route left the main path and crossed to the stream earlier in the walk and it is now easy to retrace your steps back to the start.
GLACIAL ORIGINS OF LLYN CWM LLWCH
Llyn Cwm Llwch is a small oligotropic corrie lake having a surprisingly shallow maximum depth of only 8m. At a first glance, Llyn Cwm Llwch appears to have been formed by glacial ice sculpting out a deep basin in solid rock but a closer inspection reveals this is not the case. The shallowness of the lake and the hummocky mounds which surround it are the clues to its origins. The lake is situated at the head of Cwm Llwch in a spot which receives the most shade from the sun. Here, one of the last remaining blocks of ice from the Ice Age lingered on. Rock fragments were plucked from the Brownstone crags above by freeze-thaw, a process where water in fissures in the rock freezes, expands, cracking the rock and then melts, penetrating the rock even further before refreezing. These fragments tumbled over the wasting ice mass to accumulate in a ring around its edges. When the ice finally melted, a small lake dammed by the ring of moraine was left. This process is the same as in the formation of ‘kettle-holes,’ of which a fine example can be found beneath Craig Cerrig-gleisiad.
WALK 4
Cwm Sere and Cefn Cwm Llwch
| Start | Pont y Caniedydd (SO 039 244) |
| Distance | 9.5km (6 miles) |
| Total Ascent | 560m (1841ft) |
| Map | OL12 Western Area |
This is a fulfilling mountain route that explores one of the most spectacular and wildest valleys in the Beacons and includes sections which can be demanding in snow and ice conditions. The lower reaches of the valley are well wooded and lead into an amphitheatre created by the steep northern slopes of Cribyn and Pen y Fan. A mountain stream with small waterfalls forms a foreground to Cribyn and Pen y Fan – the two highest peaks in the Beacons. The upper parts of the route can be quite serious in bad or winter conditions but a number of less demanding variations are possible. The main features of interest are the geomorphology and glaciology, the panoramic views and some archaeological sites.
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