The Grepon has a Southern (3,482 m) and Northern (3,478 m) peak, which are the highest points of a sharp granite ridge to the east of the Glacier des Nantillons above Chamonix and northeast of the Aiguille du Midi.

The first ascent was made in 1881 by the Swiss climbers Alexander Burgener and Benedikt Venetz guiding Albert F. Mummery from England.

Thus the party came back over the same route two days later and completed a traverse to the highest crag, which involved some abseiling, "a broad road suitable for carriages, bicycles, or other similar conveyances", and more spectacular final lead climbing by Venetz, who hauled Mummery to the top after he slipped halfway.

The second ascent leader, François Henri Dunod, partly brought up three ladders as he had heard stories of the difficulty of this last pitch, though it turned out there was an easier crack to the top.

With its weight of 44 kg, it was mounted on the back of a man on June 22, 1927, by eight guides of Chamonix members of the Jeunesse catholique.