Brecon Beacons or Brecknock Beacons, mountains of old red sandstone, south Wales, about 45 km (28 mi) north-west of Cardiff. The Brecon Beacons, known as Bannau Brycheiniog in Welsh, and the nearby Black Mountains and Waterfall District make up the Brecon Beacons National Park. Pen y Fan, the highest mountain in south Wales (886 m/2,907 ft) is in the Brecon Beacons, as is its twin flat-topped summit, Corn Du (843 m/ 2,766 ft). There are two Bronze Age cairns, one on Corn Du excavated in the 1970s, the second on Pen-y-Fan, excavated in the early 1990s. A popular hiking area, local income is derived from tourism, as well as from animal husbandry on small privately owned farms.