Cambrian Mountains, region in Wales, occupying much of the principality. The rugged upland region, which receives abundant rainfall, is the source of the Severn, Towy, and Wye rivers and has reservoirs supplying water to the industrial communities of southern Wales and the Midlands of England. The highest point in the Cambrian Mountains is Aran Fawddwy (905 m/2,970 ft). The isolated valleys and hills support livestock farming, mostly of sheep. The many springs arising in the valleys have given rise to spa towns, including Builth Wells, Llandrindod Wells, and Llanwrtyd Wells, and the region has a relatively high proportion of people using Welsh as their primary language. Subsidiary ranges to the south include the Brecon Beacons and the Black Mountains.