The great round barrow/cairn(?) at the summit. Yeah, pretty obvious when you consider it... The wondrous Pumlumon peeps above the shoulder of Foel Fadian (which, as well as possessing a fairly substantial barrow of its own, hosts a viewpoint dedicated to the late, great Welsh raconteur Wynford Vaughan-Thomas. Can’t say fairer than that)
Image credit: Robert Gladstone