Yr Wyddfa Sea to Summit

SEP
26
2026
A fully waymarked sea to summit ultramarathon from Caernarfon Castle to Rhyd Ddu, covering 29 miles with about 5600 ft of ascent. Professional mountain safety and medical teams support runners and finisher medals form part of the Sea to Summit Trilogy.
Sat 26 Sep 2026
29 miles 21 miles

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Yr Wyddfa Sea to Summit mountain ultramarathon

The event is a mass participation sea to summit ultramarathon from Caernarfon Castle to Bron y Feds Uchaf, Rhyd Ddu. The course covers 29 miles (47 km) with approximately +5600 ft of ascent and follows a unique route through Snowdonia, including the Watkins Path and the South Ridge for the ascent and the Ranger Path for the descent.

The route is fully waymarked with bright orange arrows and is supported by professional mountain safety staff at key locations. Medical cover is provided by a qualified on‑site team of paramedics and doctors operating from vehicles and a private ambulance. Pit Stops are placed along the course and offer water, hot drinks, salty snacks, sweets and fruit; participants are advised to carry at least 400 kcal of personal emergency nutrition.

Cut offs are applied at a 3 mph pace. Key points on the route include Pit Stop 1 at 6.7 miles, Pit Stop 2 at 12.6 miles and Pit Stop 3 at 20.8 miles, with the finish at 29.2 miles. Participants who miss the cut off at Pit Stop 2 may take an alternate shorter route to the summit covering about 20.5 miles with 5175 ft of ascent.

Mandatory kit includes an ultra running vest or multisport backpack, trail shoes, at least 1 L hydration, waterproof jacket, headtorch, survival bag, basic first aid, whistle, GPS tracker and event number. The event is part of the Sea to Summit Series and contributes to the Trilogy medal when combined with the two sister events. Visit the organization's website for the most recent information.

29 mi
Full Route
21 mi
Short Route
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