Bwlch y Groes (Pass of the Cross) is a mountain pass at an elevation of 545m (1,788ft) above the sea level, located in the county of Gwynedd, in Wales. The length and the gradient of the climb make the highest pass in Wales stand out as one of Britain’s toughest.
The pass, also known as Hellfire Pass, is located within the Aran Mountains on the edge of Snowdonia. The surface of the road is asphalted but extremely narrow. It’s one of the steepest, toughest and most spectacular climbs in the country. It’s a road of outstanding beauty – rough, weathered and remorselessly steep. It’s one of the truly definitive climbs. It was used between and after the wars by the Austin Motor Company and the Standard Triumph Motor Company to test prototype cars and their performance during hillclimbing. It’s one of the highest mountain roads of the country.
It’s said to be the highest public road in Wales. Brutal is a word used often in cycling, but there isn’t a better one to describe the climb. The ascent is 3.5km long. Over this distance the elevation gain is 385m with an average gradient of 11%. The maximum gradient is 25 per cent. The view from the pass encompasses the plain of the Dyfi valley, Cadair Idris and a close view of Aran Fawddwy. There are some narrow sections -scarcely wide enough for two cars- where if two vehicles have to pass each other, one might have to reverse for some kilometers of winding narrow road to get to a place wide enough to pass. It shouldn’t be attempted by those who don't know how to reverse.