|Location Map ( geo)|
|Distance:||4.2 miles (6.8 km)|
|Route outline (key)|
The B4599 runs along much of the former line of the A4067 in the upper Swansea Valley. It gained its number around 1980.
The route leaves the A4067 at a roundabout and runs through Ystalyfera along Ynysdarren Road, to begin with adjacent to the road we've just left. The two roads soon separate and we bear right to cross the Afon Twrch to enter Gurnos. At a roundabout by Tesco a short spur heads left to a roundabout on the A4067 and A4068 but the mainline of the B4599 bears right.
We follow the dead-straight Wind Road then bear left at a mini-roundabout to avoid crossing the River Tawe. After coming alongside the river a mini-roundabout is reached, from where another spur heads west past the rugby ground to return to the A4067 almost back in Gurnos. The mainline of the B4599 continues alongside the Tawe briefly, then bears sharply right to cross it.
We continue along Brecon Road through the centre of Ystradgynlais. The suburbs then merge seamlessly into Penrhos. After returning to open country there's a brief descent to journey's end at a roundabout back on the A4067.