Craig-y-Cilau National Nature Reserve

This former limestone quarry is one of Wales' most outstanding botanical sites, famous for its exceptional variety of alpine plants and trees, some extremely rare.

Where industry meets natural beauty

Craig-y-Cilau is no untouched wilderness. Take one look at its spectacular escarpment of limestone cliffs and its is strikingly obvious that large-scale quarrying once played a major role here. Sections of the cliff are scooped out while others remain in their natural state. It is this combination of natural and industrial history that gives the reserve its compelling character.

Perched high on the hillside above the Usk Valley, Craig-y-Cilau consists of a sweeping amphitheatre of cliffs and screes that curls around the edge of Mynydd Llangatwg. This craggy, 120m-high curtain is one of the largest limestone cliffs in South Wales. Together with its grassier, gentler lower reaches, it forms a reserve famous for its variety of plants.

In the 18th and 19th centuries, the cliffs were quarried for limestone, a key ingredient in the ironmaking process. The limestone was hauled by horse-drawn tramway – the route of which still exists – all the way to the ironworks at Brynmawr and by incline down to the Monmouthshire and Brecon Canal at Llangattock.

Two gateways into the reserve

The old tramway provides the easiest route into the reserve. Accessed from the minor road in the hills south of Crickhowell and Llangattock (or north from Brynmawr), it leads along the base of the cliffs into the heart of Craig-y-Cilau (note the stone sleepers, remnants of the original track). A second route is accessible from the Llangattock to Beaufort mountain road. Park just after the cattle grid and follow the path southwards.

Prolific plant life

The nutrient-rich limestone and inaccessibility of much of the terrain to grazing sheep have resulted in a prolific plant life. Over 250 species have been recorded here, including beech, ash, hazel, large-leafed lime and yew. The rock ledges support an interesting mix of flowering plants, while the woodland cover on the lower slopes is mainly slow-growing hawthorn, restricted from developing into large trees by the grazing action of sheep.

But Craig-y-Cilau’s undisputed jewel in the crown is the whitebeam. Many different species of these rare trees survive here. One of the rarest of all is the least whitebeam, a species unique to the locality. Whitebeams grow everywhere along the cliffs – please do not disturb them. They can be spotted by their white flowers in summer and bright red berries in autumn.

Wetland too

Craig-y-Cilau isn’t all cliff, rock and crag. At its base lies the marshy peat bog of Waen Ddu. This dome-shaped raised bog is quite rare in Wales. Peat cutting has damaged many bogs. Waen Ddu is relatively intact and still growing, though its plant cover has been grazed intensively by sheep (note the differences in vegetation in the enclosures fenced to keep the sheep out). Plants that grow here include the insect-eating common sundew.

An underground world

The reserve’s other claim to fame is its labyrinthine cave system. The action of water on limestone rock over countless centuries has produced a vast cave system – one of the largest in Europe – that can be accessed from the escarpment. The most famous entrance, Agen Allwedd, leading to around 20 miles of surveyed passageways, is locked and accessible to experienced cavers only. The cave is home to a large colony of lesser horseshoe bats.

A second cave entrance at Edlwys Faen is open and fully accessible off the tramway, though casual visitors should be suitably equipped and always accompanied by an experienced caver. In all, there are over 400 miles of discovered passages beneath Mynydd Llangatwg.

In the skies

Around 50 species of bird can be seen in the reserve. Ravens, jackdaws and peregrine falcons breed on the cliff edges and amongst the crags. Other species to look out for include buzzards, kestrels, sparrowhawks and tawny owls. The more wooded lower slopes attract tits, redstarts, garden and wood warblers, spotted and pied flycatchers and tree pipits. More than 25 species of butterfly can be seen within the reserve.

Visiting Craig-y-Cilau

The reserve is open to the public. Access is free. Some areas are rough and slippery underfoot. The weather can change rapidly. Suitable clothing and footwear is essential. Rocks regularly fall off or over the cliffs; for your own safety keep away from the foot of cliffs. The reserve is grazed by ponies and sheep for most of the year. Please follow the Countryside Code and keep dogs under close control.

A walk with a view

The high-level tramway gives grandstand views across the beautiful Usk Valley and brooding, bulky Black Mountains that straddle the English border. Cast your gaze immediately upwards to the dramatic backdrop of cliffs and you will see different bands of limestone that step up to Craig-y-Cilau’s cap of millstone grit and the moors of Mynydd Llangatwg, a wild plateau covered with heather and bilberry.

The tramway is also accessible (by a steepish footpath) from the path off the Llangattock to Beaufort road at the northern end of the reserve. An old holly tree in the middle of the reserve acts as a Piccadilly Circus for the various footpaths. From here, walkers can follow low-level paths alongside the stream and through adjoining farmland, or climb up the to tramway.

How to get there

There are access points from the unmarked road out of Llangattock which joins the B4506 road between Llangynidr and Brynmawr. Alternatively, from Llangattock, follow Hillside Road for approximately 500m, then turn right onto another very narrow, winding and steep lane that will take you up to the top of the escarpment. Once up on the top look out for another very sharp right hand turn which leads to a track at the end of the road.

Nearest town or village


OS grid reference



Roadside parking, 200m from the reserve, and a car park, a mile from the reserve.