Snowdon Sea to Summit 45k Challenge

Open dates for 2026: Summer Solstice Weekend: Saturday 20th June 2026 This event is now guaranteed to run! Our Sea to Summit walking challenge is 45km in length with over 1600 metres of ascent on a mixture of footpaths, minor lanes and mountain paths. We start at 8am at Black Rock Sands, close to Porthmadog, which has good public transport links, we then aim to finish at Pen-y-Pass within 12 hours. The Afon Glaslyn is one of Snowdonia's mighty rivers, it is steeped in local history and legends. From its source, the high mountain lake of Glaslyn, directly underneath the summit cliffs of Yr Wyddfa/Snowdon, the Afon Glaslyn cascades down through a series of gorges, lakes and valleys before reaching the flood plains of Porthmadog and the Irish Sea. The concept is simple: start at the mouth of the river and follow it, as close as it is practical, to the summit of Snowdon. We start at the iconic beach of Black Rock Sands close to Porthmadog and pass such famous sights as the Aberglaslyn Gorge, Beddgelert & Nant Gwynant on our way to the start of Snowdon's Snowdon's Watkin path. Partway up the mountain we strike off to one of Snowdon's finest routes, the South Ridge, and eventually reach the summit of Snowdon at 1085 metres above sea level. The day is not yet over, we make a quick descent of the Miner's Track before the challenge is finally over at Pen-y-Pass. What's Included: A full day of guided walking from a qualified, experienced & insured mountain leader in a small group. Assistance with local travel if necessary at the beginning and end of the challenge. Support vehicle at 3x checkpoints. Water refills, hot drinks and first aid assistance will be available - plus you can leave an extra bag with spare kit & clothing. You must arrange your own accommodation & food, contact for any help. Required Experience: Fit mountain/trail walkers & runners with experience of routes over 30km can consider signing up. Please contact if you'd like to discuss the suitability of this route. Individual bookings: Spaces are £145 per person and the full balance is payable at the time of booking. Private group bookings: Please get in touch via the contact page for availability and quotes for a private Snowdon Sea to Summit booking. Custom itineraries can be scheduled to suit you.