Think of the busiest roads in Wales and you will inevitably think of the M4 and the A55. Often overlooked is the A470 between Cardiff and Merthyr Tydfil, a remarkable road that is, by any meaningful measure, an urban motorway.
It crosses cattle grids and untamed moorland, it climbs 1-in-4 hills and plummets through hairpin bends, it runs single-track through woodland and historic villages. It's rugged and beautiful. Is it really the A39?