Le Semnoz via the Grotte des Fours

From Annecy or Alby-sur-Chéran (Rumilly motorway exit), take the D 5 to Viuz-la-Chiésaz. Park in the cemetery car park.

(S/E) Take the Route des Bauges (CD 5) northwards for 200 m.

(1) Turn right to go up the Route des Pierres to the hamlet of Les Granges.

(2) At a right-hand bend at the top of the hamlet (100 m after the altitude 726 on the IGN map), continue straight ahead on the marked path climbing south-east into the forest. Stay on the main marked path at the numerous forest track crossings in the Mottets area, until you reach the Combe Noire crossroads marked 1029 on the IGN map.

(3) Turn left to climb the path towards Semnoz, following the hairpin bends on the steep slopes in the forest.

(4) At the foot of the rocky outcrops, a junction on the left indicates the path to the Grotte des Fours (a 15-minute round trip, which will be done on the way down). Stay on the path, which passes a slightly exposed section equipped with chains to climb above the Rocher des Fours. A final steep climb takes you out of the forest and into meadows that are still partially wooded.

The path climbs up the mountain pasture along a ridge to the east, leading to the Semnoz ridge. As you approach the ridge, veer slightly to the left to reach the roadside car park.

(5) Head towards the clearly visible Crêt de Châtillon, passing behind the chalet (Courant d'Ere restaurant) and climbing the paths towards the chairlift arrival point and the summit.

(6) After taking in the view, descend either via the path you took on the way up, or by cutting south-west near a reservoir and then through the mountain pastures to rejoin the path on the grassy ridge you climbed. Descend westwards and take the steeper path through the forest to rejoin the fork in the path you took on the way up.

(4) Turn right to visit the Grotte des Fours. Follow a well-marked path northwards, which descends to the foot of the cliff and then climbs back up to the entrance to the cave.

(7) Turn back.

(4) Descend to the Combe Noire junction.

(3) Turn left towards Gruffy. The slope levels out and the path becomes a forest track.

(8) It passes near the Guindes clearing (barn) and continues downhill to a crossroads at altitude 792 on the IGN map.

(9) Leave the marked path that goes straight towards Gruffy and turn right (west) onto a forest track following the slope. Once out of the forest, the path veers to the right to join the rural path known as Les Fontaines, then the Route des Champs Blonds, which you take to the right until you reach the crossroads at the top of the hamlet of Le Buisson.

(10) To avoid too much road, do not go down into the hamlet, but cross over to the other side and walk up the gravel road a little. When it turns to the right, go down a path on the left that leads to the hamlet of Barreau and then, via its small road, to the junction of the CD 5 and Route des Bauges.

(11) Take this road to the right to the cemetery (S/E).

The climb through the forest is steady but not particularly difficult. The only section requiring attention is the chain-assisted passage above the Grotte des Fours: it is not difficult but a little exposed, without being vertiginous.
The rating of Difficult is simply due to the length and elevation gain of the route as a whole.

Except for the last part towards Le Buisson (from (9) ), the entire route is marked (usually with yellow arrows on green signs, spaced apart) with directional signs at the main crossroads.

Alternative: it is possible to reduce the elevation gain slightly by starting the circular from the hamlet of Le Buisson, at WP (10) on the GPS track: head north on the small tarmac road, then the gravel road; when it turns right towards the buildings, continue straight ahead, cross a field and go up a thalweg in the forest until you reach the forest tracks that lead to the marked path up to the Mottets area.
Please note that the paths shown on the map are often abandoned or have disappeared, so this crossing to reach Les Mottets is partly off-trail, but the forest terrain is not too difficult to cross.

The view from the ridge is extensive: Bugey, Bauges, Chartreuse, Bormes and Aravis, as well as Mont Blanc, Mont Pourri, Grande Casse, Aiguilles d'Arves, Écrins and Meije, Étendard and Belledonne-Sept Laux.

The visit to the Grotte des Fours is described on the return journey, but it can just as easily be done on the way up.
The Grotte des Maquis in this area is close to the south of the Grotte des Fours, but access is via a "via ferrata", which exceeds the "hiking" mode of this route.