Instruction 1
From the car parking spaces beneath the woods east of the Nantymoch dam (near the spot height 392m on OS Explorer maps) walk north along the road and take the righthand fork. The road descends to cross the streams of Nant Maesantfach and Nantymoch before traversing rough moorland along the east shores of Nantymoch Reservoir. The reservoir, stocked with native brown trout, is popular with anglers during the season.
Instruction 2
Beneath the quarried rocks of Bryn y Beddau, a rubble track on the righthand side of the road doubles back up the hillside then swings round to the left. The steep sides of Pumlumon now soar away to the skyline on your right, with the little stream of Maesnant tumbling down them. The track climbs further, then levels out to pass some shallow lakes, which lie above the rocks of Fainc Ddu uchaf. Now high above the bare valleys of the Hyddgen and Hengwm the track swings south beneath crags of Pumlumon Fach to arrive at Llyn Llygad Rheidol's dam.
Instruction 3
To get to the footpath along the other side you'll have to ford the stream a short way downhill - take care if the stream is in spate. The path, which runs parallel to the eastern banks of the stream, is sketchy in places, especially where you ford a side stream. It descends peaty terrain where mosses and moor grasses proliferate.
Instruction 4
When you reach a small stand of conifers in the Hengwm Valley, turn left to follow an old cart track which fords the Afon Rheidol, close to its confluence with the Afon Hengwm. The track heads west and soon the Hengwm Valley meets that of the Afon Hyddgen. The track swings to the south west and passes between the squat cliffs of Fainc Ddu uchaf and the western shores of Nantymoch Reservoir.
Instruction 5
Go through the gate above the outdoor adventure centre at Maesnant and continue along the tarmac lane used in the outward route, to return to the car park and the start of the walk.