Park in the small car park at Col du Pertus, which can be reached from Mandailles-Saint-Julien or Saint-Jacques-des-Blats.
(S/E) From the pass, follow the GR® 400 (white and red markings) north-east to an intersection.
(1) Continue on the GR® slightly to the right, through the woods until you reach a track.
(2) Continue in the same direction on the GR® which goes around the Puy de l'Usclade to the east. A few clearings allow you to see the cone of Puy Griou straight ahead. You will reach a small pass at an altitude of 1362 metres.
(3) At this pass, leave theGR® and take the green-marked path on the left that climbs uphill (towards Puy Griou via Usclade). You will reach an intersection.
(4) Leave the green markings and take the path opposite, which climbs steeply along the Usclade ridge.
This steep path passes through a small scree slope before reaching Puy de l'Usclade (altitude 1498).
(5) Return via the same route you took on the way up.
(2) Don't forget to leave the track for the path on the left to reach the Col de Pertus (S/E).