At the southern end of the National Park, Ystradgynlais is flanked by mountains - The Drum, Cribarth, Farteg and Mynydd Du - and bisected by the Tawe River on its way to the sea at Swansea. An excellent road connects the area to the M4 Motorway 12 miles down the Valley.
Man has lived in the area since at least Mesolithic times (7000-5000 BC) and many traces for this era can be seen. Standing Stones such as Maen Llia and Maen Madog, bones and other artifacts attest to human occupation. An ancient stone circle, Cerrig Duon, with its attendant standing stone, Maen Mawr, alongside the young Tawe River, are pointed to by a row or alignment of stones known as the Saith Maen or Seven Stones which lies atop the Cribarth. The early history of the area is explained in the fascinating Dan yr Ogof Caves,just past Abercraf at the head of the valley.