and there is a book ...
CAVES OF THE CENTRAL NORTHERN OUTCROP - Part 6 in the Series "Limestone and caves of South Wales" by Tony Oldham. January 2000. viii + 66 pp, 32 surveys / location maps, 2 photos. Contains such classics as Chartists' Cave, Crescent Cave, Carno Adit Cave, Ogof Rhyd Sych and Ogof y Ci etc. Covers in great detail the area between Cefn y Coed Cymmer, Merthyr Tydfil, Trefil, Beaufort and Llangynidr. Read about the hitherto secret discoveries by the Severn Valley Caving Club. Only available as a DVD ?3.00 post free in the UK.