The Brecon Beacons range, in its narrower sense comprises six main peaks: from west to east these are: Corn Du, , Pen y Fan, the highest peak, , Cribyn, , Fan y Bîg, , Bwlch y Ddwyallt, , and Waun Rydd . These summits form a long ridge, and the sections joining the first four form a horseshoe shape around the head of the Taf Fechan, which flows away to the southeast. To the northeast of the ridge, interspersed with long parallel spurs, are four cwms, four round-headed valleys or cirques; from west to east these are Cwm Sere, Cwm Cynwyn, Cwm Oergwm and Cwm Cwareli.