The route makes a circumnavigation of the Snowdon massif, starting and finishing at Llanberis.

[2] The marathon announced in June 2023 that it would be known as Marathon Eryri in future, citing the removal of the term Snowdonia by the national park authority a few months earlier.

[3] The marathon starts and finishes near the village of Llanberis at the foot of Snowdon.

From there it descends to the shore of Llyn Dinas and continues to the village of Beddgelert.

Since 2012 there has also been an annual Snowdonia Half Marathon, held in April, and mostly run on roads between Llanrwst, Trefriw and Betws-y-coed.