aerial view of cwm llwch lake below the summits of pen-y-fan and corn du in the brecon beacons, wales

llyn cwm llwch wales aerial view bannau brycheiniog beacons beautiful brecon british corn country countryside dramatic glacial lake green high hike hiking hill hills landscape llwyn mountain mountains national park natural nature outdoor outdoors peak pen fan penyfan pond ridge rugged rural scenery scenic summer tourism trail valley walking welsh wilderness summits pen-y-fan