Walk-in
From the Berneuse mountain station, head northwards down into a hollow (1,905 m) with a chairlift valley station. On paths, climb more or less along the lift run up to the grassed ridge. Traverse to the right and over a mound of scree to the start of the via ferrata (approx. 2,190 m) on the west wall, roughly in the fall line of the left of the yellow overhangs.

Tour d'Aï via ferrata
The via ferrata follows the "Voie des Vires" over a series of ledges running diagonally upwards and to the right, climbs up through a chimney, conquers a vertical to overhanging wall, follows a grassed ledge to the left, and leads over an edge to the top of the Tour d'Aï.
 
Descent
The descent uses an exposed, marked normal path over the south-east ridge, firstly bearing left of the cut over steep slopes, then over a sharp ridge of rock which widens out and becomes grassy. Finally, keeping to the left, you reach a rocky channel. At the foot of this, bear right to Chalets d'Aï (1,892 m) above the lake bearing the same name; from here you can climb again in 20 minutes to the Berneuse mountain station, or take hiking paths down to Leysin-Feydey in 1 hour.

Quelle: Eugen E. Hüsler/Daniel Anker: Wandern vertikal. Die Klettersteige der Schweiz, AT Verlag, Baden 2004