Two days from now, the streets of Llanberis will empty as hundreds of runners head uphill into the mountains of Eryri — Snowdonia's Welsh name, and one of the most dramatic landscapes in Britain. The ERYRI 25K is the entry-level race in the Ultra-Trail Snowdonia by UTMB programme, but do not let the distance fool you. With 1,400 metres of elevation gain over 25 kilometres, including a summit of Yr Wyddfa (Snowdon), this is a proper mountain race.
The Course
The ERYRI 25K is a circular route starting and finishing in Llanberis. The race climbs through two primary peaks — Yr Wyddfa at approximately 1,085 metres and Bwlch Maesgwm at roughly 600 metres. The terrain is predominantly technical mountain trails with rocky sections, exposed ridgelines, and steep descents that demand focus and sure-footedness.
The climb up Snowdon from Llanberis is relentless — roughly 1,000 metres of vertical gain in the first half of the race. The Llanberis Path is the most gradual of Snowdon's six routes, but at race pace with 400 other runners, it feels anything but gentle. The summit — if the cloud clears — offers views across Anglesey, the Llyn Peninsula, and on exceptional days, the mountains of Ireland.
The descent is where the race is won and lost. Technical, rocky, and steep, it rewards runners with strong quads and the confidence to let go downhill.
Why ERYRI Matters
The ERYRI 25K carries one UTMB Running Stone — the currency that allows entry into the UTMB Mont-Blanc ballot. For many runners, this is the gateway to the world's most famous ultra, and that gives the race an atmosphere that transcends its modest distance.
The Ultra-Trail Snowdonia programme also includes 50K, 80K, and 100-mile distances for runners seeking bigger challenges. The 100-mile features 9,600 metres of elevation gain — making UTS one of the toughest ultra-trail events in the world.
Connect with training partners, earn travel miles, and discover terrain worth crossing borders for.
Join ZealZagFollow us on InstagramWhat to Expect on Race Day
Weather: Snowdonia weather is unpredictable. May can deliver sunshine and warmth or cloud, wind, and rain — sometimes all in the same hour. Mandatory kit includes a waterproof jacket, and experienced runners carry a spare layer regardless of the forecast.
Terrain: Rocky, technical trails with some boggy sections. Trail shoes with aggressive grip are essential. Road shoes will not survive.
Nutrition: The race has aid stations but carry your own gels and a soft flask. The climb is long enough that you will need fuel before the summit.
Atmosphere: Llanberis is a trail running town with a passionate community. The start line energy is electric, and the finish line — back in the town centre — draws crowds of supporters, families, and fellow runners.
Run Snowdonia Yourself
You do not need a race bib to run these mountains. The trails are open year-round, and Snowdonia offers some of the best mountain running in the UK. Our Race the Route: Snowdonia guide covers the best routes, conditions, and how to connect with local trail runners on ZealZag.
Also happening this week: Vingegaard conquers the Blockhaus, the WSL Championship Tour hits Raglan, and the Keswick Mountain Festival runs through Sunday.