10k Run Tanygrisiau: Scenic Ascent Through Snowdonia's Peaks

Route Overview & Local Insights

This 9.9km loop through the Moelwynion range offers a rugged and rewarding challenge for trail runners looking to escape the busier Snowdonia peaks. Starting from Tan-y-grisiau, you'll tackle a significant 618m of ascent, climbing past the impressive Llyn Stwlan dam before hitting the technical Ridgeline between Moelwyn Bach and Moelwyn Mawr. The terrain is classic Welsh fell territory—expect steep, grassy climbs, rocky outcrops, and fast, technical descents on the Snowdonia Slate Trail. Reaching altitudes over 700m, this "SL" (Small Long) course rewards your effort with breathtaking views across the Glaslyn estuary and toward the Snowdon Massif, provided you are prepared for the rapidly shifting mountain weather.

Steeped in industrial heritage, Tan-y-grisiau and the Blaenau Ffestiniog area were once the "slate capital of the world." As you descend via Llyn Cwmorthin, you’ll run through a hauntingly beautiful landscape of abandoned quarries and the ruins of the Cwmorthin Terrace, where quarrymen once lived and worked in the shadow of the mountains. This route connects the wild beauty of the Moelwyns with the gritty history of the Cambrian Way, offering a unique glimpse into the heart of the UNESCO World Heritage slate landscape. Local runners know this area for its resilience and character; the climbs are tough, but the history beneath your feet makes every mile more meaningful.