Blue Lagoon
The Blue Lagoon near Llangattock, in the Brecon Beacons National Park in Wales, is a striking flooded quarry that has become one of the region's most talked-about natural swimming spots. Situated in the hills above the village of Crickhowell in Powys, the site occupies a former limestone quarry that over decades has filled with rainwater and groundwater to create a vivid, turquoise-tinted pool. The intense colour of the water — which gives the site its evocative name — is caused by high concentrations of calcium carbonate and elevated pH levels in the water, a result of the surrounding limestone geology. This same chemistry is the reason visiting authorities repeatedly warn the public that the water, despite its visually stunning appearance, is unsafe for swimming. The alkaline water can cause skin irritation, eye damage, and other health effects, and the site is periodically visited by environmental officers who issue warnings and, at times, close the area to bathers.
The quarry itself has a long industrial history, having been worked for limestone extraction that was a cornerstone of the local economy across the nineteenth and early twentieth centuries. The Llangattock escarpment and the surrounding hillsides contain numerous quarry workings, lime kilns, and old tramways that once carried stone down to the Monmouthshire and Brecon Canal in the valley below. When active quarrying ceased, the excavated pits gradually filled with water. The transition from industrial scar to accidental beauty spot happened slowly and without design — nature reclaiming the wound in the hillside in its own distinctive way, producing a landscape that feels both eerie and magnificent at once. The quarrying heritage of this escarpment is significant enough that remnants of the old tramroads and kilns are considered historically important features of the wider landscape.
In person, the Blue Lagoon is a visually arresting place. The water genuinely does glow with an almost unnatural cyan or teal brilliance on a sunny day, drawing inevitable comparisons with the famous geothermal lagoon in Iceland, though the Welsh version is rather more modest in scale and considerably colder. The quarry walls rise steeply around much of the pool, their pale grey limestone faces streaked with mineral deposits and colonised in places by hardy ferns and mosses. The atmosphere can shift dramatically with the weather — on a bright summer day the pool shimmers and the surrounding rocks feel warm underfoot, while on overcast days the water turns greyer and the abandoned quarry takes on a more melancholy, post-industrial character. Sound in the bowl of the quarry is curious and enclosed; wind often drops away and the drip of water from the rock faces carries clearly across the still surface.
The surrounding landscape places this spot firmly within the dramatic scenery of the Brecon Beacons. The Llangattock escarpment stretches along the ridge above Crickhowell, a long wall of carboniferous limestone that is riddled with cave systems underground — including parts of the extensive Ogof Agen Allwedd cave network, one of the longest cave systems in Britain, which runs beneath the hillside. Views from the higher parts of the escarpment look out across the Usk Valley, with the market town of Crickhowell visible below and the bulk of the Black Mountains rising beyond. The Monmouthshire and Brecon Canal runs along the valley floor and offers pleasant towpath walking. Crickhowell itself is a charming small town with independent shops, pubs, and cafes, and makes an excellent base for exploring the area.
Getting to the Blue Lagoon requires a walk from the surrounding road network, which adds to the sense of mild adventure and helps explain why the spot has become popular with hikers and wild swimmers despite the health warnings. Walkers typically approach from the lanes above Llangattock village, following footpaths up onto the escarpment. The terrain is rocky and can be muddy, so appropriate footwear is advisable. Parking is limited in the area and visitors should be mindful of not blocking farm access. There is no formal visitor infrastructure at the lagoon itself — no toilets, no lifeguard, no café — and the remote, unwatched nature of the site is both part of its appeal and a factor in the risks it carries. The best weather for visiting in terms of the visual impact of the water colour is a bright, sunny day, though genuinely warm weather also brings the largest crowds of people tempted to swim despite the warnings.
One of the most fascinating and somewhat paradoxical aspects of the Blue Lagoon is the way its very danger is part of what makes it compelling. Local and national authorities have periodically dyed the water black in an attempt to deter swimmers by removing the visual appeal, only for the colour to fade and visitors to return. The site occupies a curious cultural space — beloved and photographed by thousands, featured on social media and travel blogs as a hidden Welsh gem, yet officially and consistently flagged as unsafe. It represents a broader tension between public access to wild and beautiful places and the duty of care that authorities feel toward visitors who may not fully appreciate the invisible risks that lurk behind an appealing surface. For those who visit simply to look, photograph, and absorb the peculiar atmosphere of a flooded industrial ruin glowing improbably turquoise in the Welsh hills, it remains a genuinely memorable and unusual destination.