Its the amazing Collin Donnelly video, of him setting the Welsh 3000 record, back in June 1985.
He runs right across Crib Goch, almost as if its a flat and level surface, and then full gallop down its North Ridge.
From the trig point on Snowdons Summit, to the roadside in the Llanberis pass, in only 51min, taking in Crib Y Dysgyl and Crib Goch along the way.
One of the most impressive bits of fell running on the web.