The summit is a flat, boulder-strewn plateau, similar to several of the other mountains that lie in the southern Carneddau. The cliffs below the ridges are well-known rock climbs, notably Ysgolion Duon (meaning black ladders) and Craig yr Ysfa. The flat plateau means that during winter and spring, significant accumulations of snow and blizzards occur on frequent occasions. The mountain has also been noted for its long-lying snow patches in recent years, with old snow patches known to survive on its southern gullies well into July. The highest lake in Wales, Llyn Llyffant lies to the lee of the summit of Carnedd Llywelyn.