Ystradfellte

South of the main Brecon Beacons ridge the rock changes. Old red sandstone gives way to carboniferous limestone and then to millstone grit, and where a river crosses that junction it does interesting things.

Four of them do it here. The Mellte, the Hepste, the Nedd Fechan and the Pyrddin all cut steep wooded gorges through the limestone in the space of a few miles, with waterfalls at every change of rock.

The waterfalls

Sgwd yr Eira, the waterfall of snow, on the Hepste, is the one everybody comes for. The soft shale beneath the hard cap rock has eroded back far enough that a path runs along the ledge behind the falling water. You can walk behind it, and get wet doing so.

Sgwd Clun-Gwyn, Sgwd Isaf Clun-Gwyn and Sgwd y Pannwr are on the Mellte above it, and Sgwd Gwladys on the Pyrddin to the west.

The paths are steep, rooty and lethally slippery when wet, which is most of the time. People are injured here regularly and the rescue teams are busy. Proper footwear is not optional and the river should not be entered.

Underground

Limestone means caves, and this is one of the major cave districts in Britain.

Porth yr Ogof is where the Mellte disappears into the hillside through the largest cave entrance in Wales. The river runs underground for several hundred metres and reappears below. It is spectacular from the entrance and it has killed several divers and swimmers. Do not enter the water.

Ogof Ffynnon Ddu, a few miles south-west, is among the deepest cave systems in Britain and is a National Nature Reserve, accessible only to properly equipped and permitted cavers.

Above ground

The uplands around the village carry Bronze Age monuments in quantity. Maen Llia, a large standing stone in the pass north of the village, is the most conspicuous — a slab something over three metres high in an otherwise empty landscape.

There are cairns on the ridges and the remains of silica mining on the hills, where hard quartz rock was extracted for furnace linings and taken away by tramway.

The village

Small, stone, at the end of a lane, with a church and a campsite and a great deal of traffic on summer weekends.

The whole area is part of the Fforest Fawr Geopark, designated for its geology, and it is inside Bannau Brycheiniog National Park.

Parking is limited and charged at the main waterfall car parks, and the lanes are narrow. Going early or out of season is a considerably better experience.