[1] From the parking area (SN966678), turn right onto the B4518 and immediately right again along what is known as the mountain road to Aberystwyth – a highly scenic route to drive if you have the opportunity. Turn right again along the first lane you reach before soon going left through a gate, signed as a byway. Follow this track, climbing steadily north-west up the ridge and affording fine views. About 2km along, detour onto a path forking right which leads to the impressive standing stone of Maen-serth, probably of Bronze Age origin. Descend to a col and fork left to continue your descent to the road.
[2] Turn briefly left and take the next bridleway on the right, crossing a burn near a small waterfall. Follow the grassy track uphill, soon keeping right where a path goes off to the left. The track is easy enough to follow.
Once you’ve reached the highest ground it’s worth making a short detour to the right to climb up to the trig point on Crugyn Ci. At (533m/1,749ft), this is a fine viewpoint. You may be able to spot the cairns on Drygarn Fawr, the highest point in the region, to the south-west.
[3] Once you've returned to the main track, head on to a junction where you fork right, now heading steadily downhill with ever improving views of the Elan Valley and its reservoirs below.
The view of Graig Dolfaenog, the cliff above the north-east end of Garreg-ddu Reservoir, is especially striking.
At the bottom, turn left along a track past Penygarreg and down through the trees to the road at the north end of Garreg-ddu Reservoir.
[4] Go through a gate onto the Elan Valley Trail, which runs parallel to the road. From here on, route finding is very straightforward as you follow the Elan Valley Trail all the way back to the start. It’s a surfaced path all the way, and at weekends you may well meet other walkers and cyclists.
The trail leads you down the east side of Garreg-ddu Reservoir to the Foel Tower and Garreg-ddu Viaduct, beneath which lies a submerged dam.
An information panel provides more details. On the far side of the viaduct is Nant Gwyllt church, which was built by the Birmingham Water Corporation to replace the one that was covered by the Caban-coch reservoir.
The Trail now follows the north side of the Caban-coch reservoir to its highly impressive dam.
Given the scale of all the dams and reservoirs, it’s hardly surprising that over 50,000 men worked on them during their 13-year construction.
Descend to the Visitor Centre and continue along the surfaced trail to its end at Cwmdeuddwr.