This is the most popular of Craig yr Aderyn’s crags and is often used by local outdoor activity centres. The crag is divided by The Buttress route into two separate faces, north and west; the north face is clean but has some dubious rock, while the west face is much more broken in nature, and has more vegetation. The Bastions principal feature is the Diamond Wall, a large, slightly overhanging slab on the crag’s north face. There are no restrictions on The Bastion allowing year round climbing.