A confused set of fences and gates at the edge of access land appears to bear no relationship to what the map is showing me and I emerge into an area of limestone outcrops and broken pavement, in which somewhere - so the map tells me - are two cairns, the first stop of the day. Rather overshadowing everything is the panoramic view to the northeast, sweeping across the reservoir to the central Beacons peaks.
I wander around amongst the limestone for a while, not really looking in the right place and finding nothing cairn-ish. Eventually I come across the northern cairn, a turfed-over mound with limestone blocks protruding here and there. The centre of the cairn has been scooped inevitably, but not recently if the covering turf is any indication. Treasure seekers rather than walkers have disturbed this one, it seems. The view of Pen y Fan is obscured by a small stand of trees, but would otherwise be the perfect backdrop. I fail to find the other cairn and eventually decide that bigger and better sites await.