Geograph - photograph every grid square

This square is a contender for 'most interesting square in the Brecon Beacons National Park' - though of course it's always a subjective sort of thing! Two major rock types - the Carboniferous Limestone and the Basal Grit of the Millstone Grit dominate the landscape here.
The human stories here are very much bound up with the exploitation of these rocks - limestone quarries, old and new, limekilns, tramways for moving stone and mineral products, a refractory brickworks and a 'modern' (though now long-removed) mainline railway.
Oh and nature has decorated the underside of this place with Britain's deepest cave in Ogof Ffynnon Ddu (300m) and that and the surface have been designated a National Nature Reserve. Plenty here for walkers, cavers, orienteers, botanists and industrial archaeologists then.