Llyn y Fan Fach
A Welsh lake with glacial origins, a reservoir, and a folklore legend.
Llyn y Fan Fach sits at about 1,660 feet above sea level, covering roughly 10 hectares on the northern edge of the Black Mountain in Carmarthenshire, within the Brecon Beacons National Park. It is the smaller of two lakes in this mountain massif; its slightly larger neighbour, Llyn y Fan Fawr, lies around 2 miles to the east. The lake’s name means “little lake of the peak” in Welsh.
Geologically, the lake occupies a cwm carved out by a glacier that once clung to the northern face of Waun Lefrith. That peak, along with Picws Du, overlooks the water. Waun Lefrith is built from Devonian sandstones and mudstones of the Brownstones Formation, while its southern slopes are capped by harder sandstones of the Plateau Beds Formation, which form the vertical crags along the scarp’s top edge. The lake drains northward via the Afon Sawdde into the River Towy; its southern slopes feed the Twrch Fechan, Nant Menyn, and Nant Lluestau, which flow into the Afon Twrch and then the River Tawe. Large moraines lie east of the summit at the scarp’s base, below Picws Du, and also help dam the lake itself.
A well-known folk tale, the Lady of the Lake, is tied to this place. In the story, a young man from Blaen Sawdde, near Llanddeusant, agreed to marry a beautiful woman who rose from the lake, on the condition that he never strike her three times. For years they lived happily at Esgair Llaethdy near Myddfai, raising a family, and she brought with her special cattle—said to still be kept at Dinefwr, Llandeilo—along with other animals. Eventually, however, the man did hit her three times. The reasons vary: some say she laughed at a funeral, others that she cried at a wedding. Whatever the cause, she had to return to the lake, taking the cattle with her. A team of four oxen, then ploughing, followed too, plough and all, and a furrow is still said to run across Myddfai mountain to the lake’s edge as proof. The mother later came back to help and teach her sons, especially one named Rhiwallon (in some versions, Rhiwallon is the young man who marries the fairy girl). These sons eventually went to the court of Rhys Gryg of Deheubarth and became famous doctors, known today as the Physicians of Myddfai; some of their medical recipes survive in Welsh manuscripts.
Quick Facts
- Location
- Brecon Beacons National Park, Carmarthenshire: View from near Picws Du
- Outflow
- River Sawdde
- Countries
- United Kingdom
- Max Depth
- 29 m
- Elevation
- 506 m
Facts from the source article.
Lore & Background
Llyn y Fan Fach lies in a cwm gouged out by a glacier during the ice ages, on the northern face of Waun Lefrith. The lake is overlooked by Picws Du and Waun Lefrith, the latter formed from sandstones and mudstones of the Brownstones Formation of the Old Red Sandstone. The lake was enlarged by a dam built during World War I to supply water to Llanelli, with construction starting in 1914 and completed in 1919. Labour initially involved 175 navvies, later replaced by over 150 conscientious objectors. Filter beds were built and later used as a fish hatchery.
A folklore legend, the Lady of the Lake, tells of a local young man who married a beautiful girl from the lake on condition he not hit her three times. He eventually did hit her three times, and she returned to the lake, taking her cattle, including a team of oxen with a plough. The mother later returned to help and instruct her sons, one named Rhiwallon, who became famous doctors known as the Physicians of Myddfai. Their medical formulae remain in Welsh manuscripts.
The lake is accessible on foot via a water company's road from a car park near Llanddeusant. A path continues to the escarpment, reaching the summits of Waun Lefrith and Picws Du. The Beacons Way follows the ridge and provides an alternative route. Wildlife includes red kite, common buzzard, kestrel, carrion crow, common raven, skylark, field voles, foxes, and badgers.
Reader's Guide
Llyn y Fan Fach is significant for its multiple roles: as a glacial lake within the Brecon Beacons National Park, as a reservoir built during World War I to meet the water needs of a growing population in Llanelli, and as the setting of a prominent Welsh folklore legend. The legend of the Lady of the Lake is directly linked to the historical Physicians of Myddfai, a family of doctors whose medical formulae are preserved in Welsh manuscripts, giving the site cultural and historical importance beyond its natural features. The lake's construction history, involving conscientious objectors as laborers, reflects social and wartime conditions of the early 20th century. Its geology, with Devonian sandstones and mudstones, and its glacial origins, contribute to the landscape's scientific interest. The area supports diverse wildlife, including the red kite, which was once restricted to this region due to persecution. The lake remains a destination for walkers and those interested in folklore, accessible via a track from Llanddeusant, with a bothy near the dam. Its legacy endures through the continued telling of the Lady of the Lake story and the recognition of the Physicians of Myddfai in Welsh cultural heritage.
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