Mynydd Mawr

Mynydd Mawr

Summit and setting

Mynydd Mawr stands northwest of Yr Wyddfa in Gwynedd, between the Rhyd Ddu valley and the uplands above Y Fron. DoBIH records 697.5 m elevation and 462.5 m prominence. Its highest point is the cairn southeast of the wind shelter. The mountain is a Marilyn, Simm, Hewitt and Nuttall.

Rhyd Ddu via Foel Rudd

Start at the station pay-and-display car park, SH571526. Walk through the village along the A4085, turn onto the B4418 and enter the forestry track. Leave it for the climbing path near SH562540, cross the stiles and climb beside the forest to Foel Rudd. Follow the ridge around Cwm Planwydd to Mynydd Mawr. Return along the same ridge, forest path and village roads to the car park.

Walking Britain’s complete out-and-back is 9.8 km with 576 m ascent and an estimated 4 hours 40 minutes. The Rhyd Ddu Path on the opposite side of the valley climbs Yr Wyddfa and is a different walk.

From Y Fron

Begin in the centre of Y Fron. Follow the eastward road, turn left at its last junction before the cul-de-sac and continue over the cattle grid onto Uwchgwyrfai Common. Pass above Llyn Ffynhonau to the main climb near SH531555. The old mine track climbs steeply before becoming a fainter grassy path towards the summit. Retrace this route to Y Fron, taking particular care to find the upper descent and to keep clear of old workings.

Dave Roberts’ village-start route is 8.25 km, 436 m ascent and about 3 hours, including the return. Walking Britain describes a shorter 6.5 km/379 m version from SH516551 beyond the village; those figures belong to that different start.

Llyn y Dywarchen return option

Mud and Routes describes a separate circuit starting at the B4418 forestry entrance. Ascend via Foel Rudd as above. Descend the summit ridge to the forest stile, then remain outside the plantation and follow the grassy ridge down towards Llyn y Dywarchen. Follow the lake edge to the B4418 and turn left along the road to the forestry entrance. Its published figures are 9.31 km and 510 m ascent; no duration is given. Allow separately for walking from the station car park and for any optional Clogwynygarreg detour.

Access and mountain safety

The upper slopes are steep, and the rim of Cwm Planwydd has substantial drops at Craig y Bera. Stay back from cliff edges. The western path is loose in places and can disappear into grass near the top, making the descent difficult to locate in mist. Abandoned workings are another reason to keep to the route. Road sections need care around traffic.

The forest is a working landscape. Follow posted forestry closures and diversions, and keep gates and access roads clear. Carry mountain clothing, food, water and a map and compass, and check the forecast. Snow and ice require suitable winter experience and equipment.

Rhyd Ddu’s car park is beside its Welsh Highland Railway station. Sherpa’r Wyddfa S3 connects the village with Caernarfon and Beddgelert; S4 connects Porthmadog with Beddgelert. Check return services before setting out. Public toilets are listed at Rhyd Ddu; the accessible toilet requires a RADAR key according to the railway operator. Y Fron has limited roadside parking, and the community centre’s accommodation parking is not automatically available to walkers. Its operator page currently lists the café as closed.

Rock, views and heritage

BGS identifies riebeckite-bearing microgranite, an intrusion that hardened surrounding older sedimentary rocks. Slate workings on the lower western and southern flanks recall the area’s industrial past. In clear weather the summit looks across Yr Wyddfa, Moel Hebog and the Nantlle Ridge towards Anglesey, the Menai Strait and the Llŷn hills. Mynydd Mawr means “Big Mountain”.