Rhinog Fach and Y Llethr Circular

An out-and-back approach from Coed Graigddu Car Park to the Llyn Hywel basin, with a connected two-summit excursion over Rhinog Fach (about 712 m) and Y Llethr (about 750 m). Total walked distance is 9.0 miles / 14.6 km with roughly 606 m / 2,000 ft of ascent, and that figure covers the whole outing, including the shared approach walked twice. Detailed route mapping of the traversal comes out at about 9.37 miles, which is a sensible cross-check rather than a different route. Allow about 6 hours 10 minutes moving, and realistically 6 to 7 hours with stops and slow going on rock.

• Follow the rough access track south from the car park, then branch through the forest onto open fell.
• Continue past Bwlch Drws Ardudwy, the deep pass between the Rhinogydd.
• Climb gently past small mountain lakes including Llyn Cwmhosan to reach Llyn Hywel.
• Take the rugged side of Rhinog Fach to the summit, then return to the col.
• Climb the rounder, grassier Y Llethr, then descend a pathless grassy line back toward Llyn Hywel.
• Retrace the outward approach to the car park.

This is hard mountain walking, rated 8 out of 10. Expect steep boulder and scree slopes, rough rocky ground, boggy patches and genuinely pathless sections on Y Llethr. A few moves on Rhinog Fach can feel like easy scrambling, and there is real exposure on the rocky ground above Llyn Hywel. The route passes into the Rhinog National Nature Reserve, where there are no path markers and the ground is often very wet, so carry a map you can actually use and wear strong waterproof footwear. Confident navigation matters more here than fitness alone.

The payoffs are concentrated in the high basin: Llyn Hywel cupped under crags, the boulder slopes and slabs of Rhinog Fach, the two summits, and broad views out over the mountains toward the coast. From the summit of Rhinog Fach you look down on Llyn Hywel and Llyn Perfeddau. For pictures, the lake and crag combination reads best in low, angled light early or late in the day, when the rock texture and the slate and heath colours separate; from Y Llethr you get the classic view back across the water to Rhinog Fach. Build extra time into the day if you want to wait for light, because this is not ground to hurry down.

The durable pattern is simple: the exposed rocky ridge, boulders, scree, soft ground and weak paths make wet, windy or low-cloud days materially harder and slower, and route-finding on the pathless descent gets much more serious in poor visibility. Longer daylight and drier spells make the crossing far more pleasant. Winter snow and ice call for proper mountain experience and equipment, including the skills to use it.

Coed Graigddu Car Park (near SH684302) is the start and finish, with free designated parking. Use the designated spaces and do not block field gates or residential entrances. Dogs are welcome on public footpaths and open-access land, kept under close control, on a short lead near livestock and wildlife. Eryri National Park guidance requires a lead of no more than 2 m on open-access land from 1 March to 31 July.

You walk the same approach twice and gain the summits by steep, rough, unmarked ground, so this is a long day for two tops. In exchange you get one of the quieter, more rugged corners of the Rhinogydd, with dark mountain lakes, rock and heath, and views that feel earned. If that sounds like more than you want, the shorter walk to Bwlch Drws Ardudwy from the same car park covers the gentler part of the same ground.