Carmarthenshire Fans Hiking Guide: how to visit LLyn y Fan Fach and Fawr
Llyn y Fan Fach (which translates from Welsh as “Lake of the Small Hill”) is an enchanting glacial lake, set beneath the steep, flat-topped ridges of the Carmarthenshire countryside.
Tucked away on the western edge of the Brecon Beacons, this is a lesser-known gem, but in my opinion, it’s one of the most beautiful spots in Wales and easily my favourite hike in the entire National Park.
Although slightly more difficult to reach than the popular Pen-y-Fan, this breathtaking area epitomises the beauty of the Brecon Beacons and should definitely be on your ‘must visit’ list.
Just to the east lies its larger sibling, Llyn y Fan Fawr, the “Lake on the Big Hill.” Not only is it the source of the River Tawe, but it’s also a popular wild swimming spot. While not quite as dramatic as Llyn y Fan Fach, it’s still well worth including if you’re planning a longer hike.
This region offers up a variety of walking routes of different lengths and difficulty levels, making it perfect for hikers of all abilities, from families with children (or even a sturdy pushchair) through to those chasing big summit days.
So read on for everything you need to know about visiting, from parking, and route options to the best peaks and viewpoints along the way.
Where to park for LLyn y Fan Fach
The easiest access point for Llyn y Fan Fach is a small gravel car park tucked away in the rolling Welsh hills just outside Llanddeusant (postcode: SA19 9UN).
Getting there can feel a bit like an adventure in itself. The route takes you down narrow country lanes that twist through farmland, and at times it almost feels like you’re about to pull into someone’s driveway. But don’t worry, if you follow the postcode it will bring you to the right place in the end.
The car park itself is fairly small, with space for around 50 cars. Because of this, and the tight country roads leading in, it’s a good idea to arrive early. Not only will this give you a better chance of securing a space, but it’ll also help you avoid awkward stand-offs with cars trying to squeeze past in the opposite direction.
The different Hike Options Available at Llyn y Fan Fach
One of the best things about starting at Llyn y Fan Fach (via the car park at Llanddeusant) is the sheer variety of walking options available. Whether you’re after a short stroll or a challenging full-day adventure, there’s something here for all ages and abilities.
The 2km path up to the lake itself is made up of hard-packed gravel. While it is fairly steep in places (with around 230m of elevation gain), it has no steps and is wide enough for a sturdy pushchair that can handle rougher terrain.
Once you reach the lake, you can choose from a range of routes:
Llyn y Fan Fach: Easy-Moderate / 4.5km / 230m / 1-3 hours / OS Maps Route
Llyn y Fan Fach and Waun Lefrith: Moderate / 6km / 400m / 2-3 hours / OS Maps Route
Llyn y Fan Fach and Picws Du Circular: Moderate / 9km / 531m / 3-5 hours / OS Maps Route
Llyn y Fan Fach, Picws Du, Fan Brycheiniog: Hard / 11km / 683m / 3-6 hours / OS Maps Route
Llyn y Fan Fach and Llyn y Fan Fawr full loop: Hard / 14km / 757m / 4-7 hours / OS Maps Route
So whether you’re just looking to enjoy the tranquil waters of Llyn y Fan Fach or you’re aiming for the summits of Picws Du and Fan Brycheiniog, there’s a walk here to suit you.
Llyn y Fan Fach & Waun Lefrith
From the car park, pick up the gravel track that follows the River Sawdde for about 2km as it winds gently uphill towards Llyn y Fan Fach. Along the way you’ll pass a series of small waterfalls and a brick building beside a water station – a reminder that this lake still serves as a reservoir.
Once you reach the lake, you’ve got a choice: you can complete the loop in either direction, but I’d recommend going anti-clockwise (turning right). That way, when you eventually reach the saddle beneath Picws Du, you’ll have the option of extending your walk further.
After taking a moment to enjoy the views at the water’s edge, follow the trail on the right-hand side. It climbs steadily, gaining around 600ft of elevation in just under a mile. The path hugs the ridgeline, giving you sweeping views back over Llyn y Fan Fach and across the Carmarthenshire Fans.
At the top you’ll reach Waun Lefrith (677m) – the most westerly peak of the Carmarthenshire Fans. From here, the dramatic escarpment of the Black Mountain range begins to unfold, and the hike really starts to show off its best scenery.
Looking back towards Picws Du From Waun Lefrith
Picws Du
From the summit of Waun Lefrith, simply continue along the ridgeline path for about a mile. The trail hugs the dramatic glacial escarpment and climbs gradually towards the striking peak of Picws Du.
At 749m, Picws Du is the second highest summit of the Carmarthen Fans, in the Carmarthenshire section of the Black Mountain range. It’s a spot well worth taking your time over as the 360° views stretch across the western Brecon Beacons. It’s a perfect place to pause, rest your legs, and tuck into whatever snacks you’ve packed.
In fact, Picws Du is often considered one of the best places in the Brecon Beacons to watch the sunset, and it’s a popular wild camping spot. I’ve stayed up here on two occasions and had an incredible sunset.
From the summit, you can either retrace your steps along the ridge, passing Waun Lefrith before descending back to Llyn y Fan Fach, or drop down the steep slope on the opposite side towards a saddle marked by a small stream.
Sunset from Picws Du, looking towards Llyn Y fan Fach
The Saddle between Picws Du and Fan BRycheiniog
Once you reach the saddle, you have two main options: either extend your walk by heading up onto Fan Brycheiniog (802m) and on towards Llyn y Fan Fawr, or descend to complete a loop back to Llyn y Fan Fach.
Even if you’re not planning on tackling the full climb, it’s worth heading a short way up the western slopes of Fan Brycheiniog, the views of Picws Du from here are incredible, and it’s a perfect spot to stop for photos.
If you’re choosing to complete the loop back to Llyn y Fan Fach, take the zig-zagging path that drops down from the saddle. When the trail splits, keep left and follow it as it traverses the lower slopes of Picws Du. Continue along this track until you reach Llyn y Fan Fach again, before descending the initial gravel track back to the car park.
If you decide to continue on towards Fan Brycheiniog, follow the clear ridge path that skirts the edge of the mountain. As you climb, the views back towards Picws Du only get better. The trail naturally curves along the ridgelines towards the summit, though if you prefer, you can make a more direct ascent by cutting across the uneven heather to reach the trig point at the top.
Fan Brycheiniog
Fan Brycheiniog is the highest peak in the Black Mountain region of the Brecon Beacons National Park, standing at 802.5 metres (2,633 ft). The summit is marked by a trig point and a small stone shelter, perched dramatically on a glacial-carved escarpment. From here you’ll find breathtaking views across the rolling moorland, over Llyn y Fan Fawr, and on a clear day all the way to the Bristol Channel. You can even see across towards Pen y Fan, the highest peak in South Wales.
When it comes to the descent, you’ve got options. You can retrace your steps back to the saddle beneath Picws Du and loop around to Llyn y Fan Fach, or you can drop down directly to Llyn y Fan Fawr to complete a circular route. Both choices reward you with sweeping scenery and the chance to experience the best of the Black Mountain’s rugged landscape.
Llyn y Fan Fawr
Situated at the foot of Fan Brycheiniog, Llyn y Fan Fawr is the larger of the two glacial lakes in the Black Mountain range of Bannau Brycheiniog. Its name translates as “lake on the big hill”, and as well as being one of the largest glacial lakes in South Wales, it’s also the source of the River Tawe.
Compared to its neighbour Llyn y Fan Fach, this lake is a little more exposed to the elements, but that doesn’t put visitors off. It’s a popular spot for wild swimming, especially since it isn’t used as a reservoir by Welsh Water, making it a natural choice for those seeking a refreshing dip in stunning surroundings.
Return to Llyn y Fan Fach
From Llyn y Fan Fawr, follow the path that skirts around the lake to its northern shore. From here, the trail begins to rise steadily as it loops back along the Black Mountain range. There are plenty of paths criss-crossing this section, which can get a little confusing, but as long as you stick to one that continues upwards and around the mountain, you’ll be heading in the right direction.
Eventually, you’ll reach a broad saddle, where the views open up and you’ll be able to spot Llyn y Fan Fawr again below. From here, follow the wide grassy track that descends back down towards the lake, and then continue along the path to return to the car park.
Final Thoughts
Whether you’re here for a short stroll up to Llyn y Fan Fach, a wild swim in Llyn y Fan Fawr, or a full day exploring the dramatic ridgelines of Waun Lefrith, Picws Du and Fan Brycheiniog, this corner of the Brecon Beacons never disappoints.
It might not have the fame of Pen y Fan, but that’s part of the magic , fewer crowds, wilder landscapes, and a sense of stepping into somewhere truly special. From glacial lakes to sweeping escarpments, hidden waterfalls to unforgettable sunsets, it’s the kind of place that stays with you long after you’ve laced your boots back up at the car.
If you’re looking for a hike that blends challenge, beauty, and a real taste of Welsh wilderness, then Llyn y Fan Fach and its surrounding peaks should be right at the top of your list.
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For more hiking inspiration check out my other guides to the Brecon Beacons below.
Central Brecon Beacons
Western Brecon Beacons
Waterfall Country
Eastern Brecon Beacons
You can find more Welsh hiking inspiration in the following blogs
For more travel, hiking, & photography inspiration around Wales check out my in-depth guides to each of my favourite regions below.
