Col de la Croix de Fer

Col de la Croix de Fer is a high mountain pass in the French Alps linking Le Bourg-d'Oisans and Saint-Jean-de-Maurienne.
The approach from the northeast from Saint-Jean-de-Maurienne is 29.5 km at an average gradient of 5.5% with some sections at 9.5%, and the one from the southwest from Rochetaillée 31.5 km at an average gradient of 5.75% with short sections in excess of 11%. When coming from Rochetaillée, the road forks 2.5 km before the summit, leading to the Col du Glandon. There is also an approach from the north from La Chambre via Col du Glandon which is the hardest: 22.7 km at an average gradient of 7.0% .

Wikipedia