An ascent of Pen Y Fan, on the A470 above Merthyr Tydfil comes highly recommended.
This was my regular walking country many years ago.
If you approach from Cardiff, head for Pontypridd on the A470, this is the main dual carriageway that leaves Cardiff, and heads towards the famous South wales valley's, follow this road and you will eventually reach Merthyr Tydfil.
Follow the heads of the valley road (A470) from Pontypridd , and eventually you will see the signpost for Brecon, just after Merthyr.
Follow the A470 towards Brecon, and in about nine miles, past the Beacons reservoirs, you will arrive at the Storrey Arms.
Park safely in the carparks provided, and climb the tallest mountain in Southern Britain, its not far off 3000ft in height, but in good weather, is very straight forward, and safe.
All the best AND WELCOME TO CYMRU