Llyn y Fan Fach and Llyn y Fan Fawr Circular Walk

Tracy Purnell By Tracy Purnell


15 km / 9 miles


4 hrs  30 m

OS Champions adventure

Medium difficulty

Free parking at Llyn y Fan Fach Car park, Llangadog, Llanddeusant SA19 9UN

OS Champion Tracy Purnell takes us on a half day circular walk across Llyn y Fan Fach and Llyn y Fan Fawr in the Brecon Beacons National Park (Bannau Brycheiniog).

Views across the Black Mountain Range Brecon Beacons National Park

The Western Beacons also known as the Carmarthenshire Fans or the Black Mountain Range (not to be confused with the Black Mountains to the east of the national park) has to be the most remote area of the whole of the Brecon Beacons National Park (Bannau Brycheiniog).

Fan Brycheiniog (a peak which stands at 802.5 metres) is the highest point in the Black Mountain Range and is marked by an OS triangulation pillar. This route is a scenic low level and high level ridge way walk, which also passes by Llyn y Fan Fach and Llyn Y Fan Fawr, two beautiful lakes surrounded by amphitheatre like escarpments.

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Sign at starting point of the route

The walk starts at Llyn Y Fan Fach car park in Llanddeusant. The road leading to the car park is narrow and the road surface extremely uneven so please take care when driving to the start of the walk. As soon as you step out of your vehicle you are welcomed by a tranquil haven, surrounded by shapely hills with the river Afon Sawdda flowing by.

Please keep your dogs on a lead throughout this walk as there are sheep in this area, some may be out of sight behind banks of the river or in low level areas. The high escarpments may also pose a hazard to off lead dogs and there are areas of loose rock at the edges. Stick to the path and ensure your dog is kept close to stop the risk of falling over the edge.

The start of the walk takes you south alongside a picturesque river drawing you towards the first lake Llyn y Fan Fach, which is the source of Afon Sawdda. The sharp peak of Picws du can be seen in the distance and looks more and more impressive as you draw close. You will pass by a small fishery and some beautiful waterfalls on route.

Waterfalls at start of the route Waterfalls at start of the route Waterfalls at start of the route

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The building at the top of the path is a rescue hut and offers emergency shelter to walkers in extreme weather conditions. However this stone building will be the last thing that captures your attention as the beautiful lake Llyn y Fan Fach comes into view.

Surrounded by the amphitheatre like escarpment of Bannau Sir Gaer, the enchanting Llyn y Fan Fach is famously known in Welsh legend as home to the lady of the lake.

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Lake view

The footpath along the ridge is well defined, as it sweeps around the edges of the contoured peaks, this is the ideal spot to take in the jaw dropping views. In the distance to the north the Cambrian Mountains can be seen on a clear day, behind a patchwork of fields and small farm dwellings.

The view to the south is vast open moorland of shake holes and rock, many of which lead into small cave systems.

Open moorland
Open moorland

The area is so enchanting, even on a misty day it adds to the atmosphere and feel of place.

There are areas of loose scree along the ridge, take care not to get to close to the edge, especially on a misty or windy day when the height can be deceiving and there could be a risk of becoming blown over.

Dogs looking out to view
Views across the mountains

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The summit of Picws Du (the second highest peak in the Black Mountain Range) is marked by a bronze age round barrow. On a clear day the view south from this peak reach as far as the Bristol Channel. The body of water to the north is the Usk Reservoir.

Continuing east along the ridge, the path descends into a small valley, the route continues across a narrow stream to a sharp ascent towards Fan Foel.

Sharp ascent towards Fan Foel

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Fan Foel has a Bronze Age burial mound at its summit. Only in recent years has it been excavated. Cremated bones, a broken pottery urn and flint tools where found within a cist, and are now at Cardiff University being conserved.

The monument and surviving elements have now been protected beneath matting and backfilled with stone and earth.

Summit overlooking lake

The next lake to come into view is Llyn y Fan Fawr, translates from Welsh as ‘lake of the big peak’. It lies beneath Fan Brycheiniog and was created due to glacial movement during the ice age. It is one of the largest lakes in South Wales.

View from Fan Foel looking west towards the peak of Picws Du and the Cwm of Llyn Y Fan Fach.

View from Fan Foel looking west towards the peak of Picws Du and the Cwm of Llyn Y Fan Fach.

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Although the whole of this ridge walk boasts impressive views, the panoramic view at the OS triangulation pillar on the summit of Fan Brycheiniog has to be my favourite.

The peaks of Fforest Fawr area, Central Beacons and the Black Mountains can be seen laid out in a row. The famous humps of Pen y Fan and Corn Du sit centre stage of the surrounding beacons.

Trig pillar at summit

Heading east passed the OS triangulation pillar and the stone shelter, the path drops down to the start of the rocky descent to the shore of Llyn y Fan Fawr.

A defined stone path takes you down to the lake which is maintained by the national park. It is a steep ascent, take care where there are sections of loose scree.

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Sunrise at lake side of Llyn y Fan Fawr

Sunrise at lake side of Llyn y Fan Fawr

Sunrise at lake side of Llyn y Fan Fawr

Sunrise at lake side of Llyn y Fan Fawr

The surrounding area of Llyn y Fan Fawr is marsh land and can be extremely boggy. There is a path which leads you around the lake, however it is not well defined. Walk around the far side of the lake and head west, to continue the low level route back to Llyn y Fan Fach.

The low level section of this walk skirts close to the base of the escarpments, the path is narrow in places and the section below Picws Du runs directly under a cliff face with loose scree under foot. This section can be avoided by walking across the marsh land below, but it can be boggy in places.

Looking back towards the narrow path below Picws Du

Looking back towards the narrow path below Picws Du

Looking back towards the narrow path below Picws Du

Looking back towards the narrow path below Picws Du

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The path takes you away from the base of the escarpments towards a man made water course, which will lead you back to the rescue shelter at Llyn y Fan Fach.

The journey continues back to the car park along the riverside path.

Journey back to car park along riverside

Edited: 03/09/2020



Tracy Purnell By Tracy Purnell


Tracy is an avid mountain walker, photographer and trig pillar obsessive.

Find out more about Tracy Purnell.