AA Walks: Along the WaterfallsIn a National Park justly renowned for its sweeping, but barren, mountain scenery, lovers of high ground are in danger of completely overlooking one the Brecon Beacons’ hidden gems. This is the pocket of dramatic limestone scenery often referred to as Waterfall Country. South of the upland plateaux of Fforest Fawr, geological faults and water erosion have produced a series of deep, narrow gorges, sheltered by impressive woodland and randomly broken up by a succession of gushing waterfalls. The highlight of this is Sgwd yr Eira, where it’s possible to venture right behind the falls. Walking here is a completely different experience to that of the windswept scarpments, but the scenery is marvellous and the generally sheltered nature of the terrain makes it an ideal outing for those days when cloud obscures the peaks. Hard Sandstone Shelves In simple terms, the falls are the result of a geological fault that pushed the hard sandstone, which makes up the backbone of most of the National Park, up against softer shales. The force of the rivers, which spring up high on the mountains of Fforest Fawr, has eroded the shales leaving shelves of the harder rock exposed. These shelves are clearly visible on most of the waterfalls.Caves and Sinkholes. At the southern edge of the high ground, a layer of carboniferous limestone overlies the old red sandstone. This younger rock is soluble in the slightly acidic rain and river water that constantly pounds it. The erosion results in caves like Porth yr Ogof at the start of this walk, where the rivers literally disappear underground, and craters where rainwater exploits weaknesses and faults in the rock - these are often referred to as sinkholes or shake holes.While you're there: Porth yr Ogof is accessed by following the steps down from the rear of the car park. You can walk in far enough to see thePool of the White Horse, named after a strip of white calcite on the wall. Legend says it formed after a princess rode her horse into the cave while evading murderous pursuers. The horse fell and she drowned. Great care is needed around the cave entrance, as a fall could be fatal.What to look for: While the woods that line the river banks are home to many species of birds, the river itself is likely to offer sightings of the dipper. This bird is easy to spot, because it is dark brown and slightly smaller than a blackbird with a very visible white bib. It’s usually seen bobbing up and down on rocks in mid-stream.AA Walks: Along the Waterfalls251.4246248.6245.6236.9229.8231.4232229.5229.4238.2239.3225.4230.9228.9226.6220.5215.8214.8214.1224.4232.2234.9233.7241.9240.9244.1255.3257.1255.4246.8243.7227.8193.9227.8228.7224.5224.5222.9221.8209.1211.2195.7201.8146.3201.8199.8201.2187.6168.7163.5163.3173.6197.7173.6163.3163.5168.7187.6201.2199.8201.8195.7211.2209.1221.8226.3229.9227.4231.7234.4226.1231.3212.2232.4227.3227.3216.9219.9220.1218.7221.4226.7228.2232.2224.4214.1214.8215.8220.5226.6228.9230.9230.9225.4239.3238.2229.4229.5232231.4229.8236.9245.6248.6251.4