On the southern most boundary of the Brecon Beacons National Park is Mynydd Garn Wen and at its highest point theres a triangulation point. Trig points, as they're commonly known, are a legacy of Ordnance Survey work from the days when field mapping was conducted by theodolite and ranging pole. Today aerial photography and GPS has rendered these as redundant as a Jessops sales adviser.
The trig point here is set on a bed of exposed and weathering quartz conglomerate. Large angular blocks of pebblely stone support bryophytes and lichens while fragments of eroded quartz scatter the upland landscape.