Carmarthenshire Fans, western Bannau Brycheiniog National Park, Wales
Llyn y Fan Fawr
Lake
Source image
8.5
Wildland
1–2 hours
Time
Check
Cost
Dramatic
Feel
Why it's Wildland
8.5A mountain lake beneath Fan Brycheiniog, reached across boggy hillside rather than a neat lakeside path.
The attraction is the scale of the setting: open water beneath the Carmarthenshire Fans, with mountain country continuing far beyond the shore. A relatively short walk brings a substantial landscape reward, but the faint paths and river crossing demand more care than the distance suggests.
Dramatic · Wild · Big-sky
Find your way
Open mapCarmarthenshire Fans, western Bannau Brycheiniog National Park, Wales
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The experience
Walk up from the eastern roadside start, cross rough hillside and reach the shore beneath Fan Brycheiniog. Stop for the view across the water before retracing the short approach. Experienced mountain walkers can make a separate full-day circuit linking both lakes and the high ridgeline.
Things to do
Walk the short eastern approach
The AllTrails route is a 2.7-mile out-and-back with 629 ft of ascent. It is rated moderate, but boggy ground, faint paths and the River Tawe crossing are significant practical considerations. Do not attempt it when the river is in spate.
1.5–2 hours
Take in Fan Brycheiniog from the shore
The short approach finishes with views across the lake towards Fan Brycheiniog. Make this the main pause of the walk: the relationship between water and mountain is the reason to come.
Link both lakes on a demanding mountain circuit
A published 16 km eastern loop links the two lakes with Picws Du, Fan Brycheiniog and Waun Lefrith. This is a hard mountain walk, not a casual lakeside extension. Consult the complete route and forecast before committing.
5–7 hours
Make a day of it
Quick escape · 1.5–2 hours walking; allow extra for stops
Quick escape: the lake beneath the mountain
- 01
Use the eastern roadside start for the published AllTrails out-and-back, checking its map before setting off.
- 02
Check the River Tawe before crossing. Do not attempt the route in spate or if the crossing is unsafe.
- 03
Follow the rough, sometimes indistinct approach uphill to the lake, using a map and compass rather than relying on a continuously obvious path.
- 04
Pause at the shore for the view of Fan Brycheiniog, then retrace the approach.
Full Wildland day · 5–7 hours walking
Full mountain day: two lakes and the Carmarthenshire Fans
- 01
Plan the separately published 16 km eastern circuit, rated hard, rather than improvising an extension to the short lake walk.
- 02
Start early at the eastern grassy lay-by identified in the guide as magically.manage.developed; parking is extremely limited.
- 03
Only proceed if the River Tawe can be crossed safely. Follow the guide's Nant-y-Llyn approach, with waterfalls along the way.
- 04
Use the full route map to link Llyn y Fan Fawr and Llyn y Fan Fach with the high ground of Fan Brycheiniog, Picws Du and Waun Lefrith.
- 05
Complete the mapped loop within daylight. Carry suitable mountain equipment and navigation; postpone in unsuitable weather.
Verified history
The supplied walking accounts describe Llyn y Fan Fawr and neighbouring Llyn y Fan Fach as glacial lakes. Their story here is primarily one of landscape: water held beneath the steep mountain ridges of the Carmarthenshire Fans. The supplied evidence does not establish a detailed human history for Llyn y Fan Fawr.
Hidden details
Waterfalls on the Nant-y-Llyn approach — The longer eastern circuit follows a faint path beside Nant-y-Llyn and passes several waterfalls. These belong to that particular approach and should not be promised as a feature of every short route to the lake.
When to go
· Early morning for a better chance of finding space in the limited parking; allow enough daylight for the chosen route.
The source row recommends spring and summer. The walking guides make ground conditions, river levels and navigation the more important considerations; no precise seasonal peak is established.
Expect boggy ground and indistinct paths. Wear walking boots and carry a map and compass. The Tawe crossing can become difficult at high water and must not be attempted in spate. The short route is listed as having no shade; check the mountain forecast before a high-level extension.
Worth pairing with
Llyn y Fan Fach
The worthwhile companion lake for a properly planned mountain day. The supplied eastern circuit links it with Llyn y Fan Fawr and the ridgeline in 16 km, taking 5–7 hours. It is not a quick add-on to the short shore walk.
What to look for
- 01
The profile of Fan Brycheiniog above the water
- 02
the contrast between the lake basin and the open eastern approach
- 03
waterfalls beside Nant-y-Llyn on the separately described longer eastern route.
Best time to go
Spring and summer for the shorter lake visit; choose settled weather and low river levels.
An early start helps with limited parking. Spring and summer are the source row's suggested seasons, but settled weather, visibility and river conditions matter more than the month. Avoid this approach when the Tawe is in spate.
How long to spend
1–2 hours
Perfect for
Walkers · Photographers
Practical information
Opening & access
Reached on foot over rough, often boggy ground from limited roadside parking east of the lake. The published short approach crosses the River Tawe: do not attempt it when the river is in spate. Paths can be indistinct; check conditions and carry a map and compass.
Check before visiting
Parking
Limited roadside parking on the eastern approach. The short-walk guide locates its trailhead at 51.882572, -3.668088 and recommends arriving early. The longer eastern circuit uses a separate small grassy lay-by; do not confuse the two starts.
Toilets
Check before visiting
Check before visiting
Food & drink
The source row reports no food or drink services on site. Bring your own provisions.
Dogs
Check before visiting
Check before visiting
Accessibility
Published approaches involve rough, boggy and sometimes steep ground, indistinct paths and a river crossing. This is not a surfaced lakeside stroll. Check before visiting for individual access requirements.
Check before visiting
Water
Lake
Gallery
Place photographsKeep exploring
Around Llyn y Fan Fawr
Within 50 km · approximate straight-line distances
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