Trou de la Mouche

A La Clusaz walk posted on 31/08/18 by Alwayswiththehills. Update : 04/09/18

A steep walk to a natural rock arch, the Trou de la Mouche (Fly Hole). The section up to the Trou is steep and loose in places, the initial descent is also steep but soon eases off. This route, although shown on IGN maps, is not marked with paint flashes. Signposts at the start of the route make this clear so make sure you have a map and compass.

The walk is best done in the direction described, and best done a clear, dry day.

Technical sheet
Calculated time Calculated time: 5h00[?]
Distance Distance : 8.85km
Vertical gain Vertical gain : 1048m
Vertical drop Vertical drop : 1046m
Highest point Highest point : 2432m
Lowest point Lowest point : 1438m
Very difficult Difficulty : Very difficult
Back to starting point Back to starting point : Yes
Walking Walking
Areas Areas : Alps, Aravis et Bornes
Location Location : La Clusaz (74220)
Starting point Starting point : N 45.922571° / E 6.484072°
Map IGN Map (Click to buy) : Ref. 3430ETR
Download :


(D) Park at the Lac des Confins, get there early in order to secure your parking place.

Follow the track towards the Chaine des Aravis and at a pasture with a barn you will see a signpost pointing out the route. (1) (Note this route has no paint flashes and only one other marker)

Follow the path diagonally up and across the pasture heading towards the ridge on the left of the Combe du Grand Cret (as you look up), the path soon turns right and heads up with zig zags through grass and then scree into the Combe proper with the cliffs of Pare de Joux on your left. Look out for the huge cave in the wall of this cliff.

One solitary arrow painted on a boulder (2) (approx position) amongst the scree points you rightwards as you continue to follow zig zags through grass now heading across the Combe towards the right hand side (as you look up).

The path turns left again and ascends with more zig zags to an easier angled section where there is a large boulder with a memorial plaque. You should be able to see the Trou up on the ridge on your right. From this point the path leads you back right again towards the foot of a spur coming down from the Trou. Depending on when you do this walk there may be patches of snow that you have to cross and in spring the route may be icy in places.

Turn left again (3) and follow the spur which is broad at first but which gets narrower and steeper the higher you get. At point(4) if you look at the satellite view you will see that the path in the scree becomes less prominent and in fact there are many small tracks from this point on. The terrain in steep, loose and slippery when wet; in bad weather and particularly in descent this section could be dangerous for those with little mountain walking experience. Ascend from point up, carefully zig zagging and picking the best way up the spur, to the Trou. From some angles it looks like two rock arches but there is a large boulder in front with creates this illusion. The Trou (5) is a good place to eat your sandwiches and enjoy the view.

As you walk through the Trou and into the Combe de Paccaly the path is quite gentle at first but it seen becomes very steep. However the rock is better on this side and steep section is not long and soon the angle eases off again at (6). There are good views to be had either side of the main Aravis ridge during this part of the descent. Keep following the along the ridge and most likely over some snow patches until the path turns left (7) and heads downwards, over scree, into the Combe de Paccaly. The path is easy to follow as you zig zag down wards, at first through scree and then into high pasture. At point (8) the path turns right and heads diagonally downwards to Paccaly d'en Haut (9). At this point there is a small building and signposts. Turn left and follow the good path beneath the combes, past buildings at Paccaly and La Bottiere back the the first pasture and then the car park.

Waypoints :
D/A : km 0 - alt. km 0 - Parking at Lac des Confins
1 : km 0.45 - alt. km 0.45 - Take path up across pasture
2 : km 1.66 - alt. km 1.66 - Painted arrow on boulder
3 : km 2.89 - alt. km 2.89 - Turn left and follow spur
4 : km 3.49 - alt. km 3.49 - Path becomes less prominent
5 : km 3.62 - alt. km 3.62 - The Trou
6 : km 3.79 - alt. km 3.79 - End of steep section
7 : km 4.22 - alt. km 4.22 - Follow path down to left
8 : km 5.96 - alt. km 5.96 - Follow path to right
9 : km 6.42 - alt. km 6.42 - Small building and signposts
D/A : km 8.85 - alt. km 8.85 - Parking at Lac des Confins

Useful Information

This is a walk in a high mountain range. Unusually for the alps it is not marked with paint flashes and whilst the path is easy to follow there are sections which are steep and loose. Inexperienced walkers and those with no heads for heights will find the section up to and down from the Trou very challenging. This route has not been marked because of these challenges and potential hazards.

Please wear appropriate footwear, mountain boots are recommended. In spring when there will be a lot of snow you will need crampons and an ice axe; but you must know how to use them.

We did this walk in August, there were still patches of snow high up which had to be crossed, half way up the cloud came down and then rain. We navigated up in poor visibility and it was very wet and slippery underfoot, in these conditions the descent from the Trou into the Combe du Grand Cret will be potentially dangerous and it is safer to follow the route into the Combe de Paccaly and descend the way described. Alternatively if find yourself in the same conditions and are inexperienced it is safer to turn around and save the walk for a better day.

You will see other people on the walk, from both directions but not as many as on the other Combe walks such as the Lac de Tardevant.

We advise taking IGN maps with you on this walk. Click here to buy : 3430ETR.

Hikideas and this author cannot be held responsible in the case of accidents or problems occuring on this walk.

During the walk or to do/see around

On the way up enjoy the scenery as you ascend the Combe. Look out for the massive caves and keep your ears and eyes open for marmots and other wildlife.

Enjoy the views from the Trou and across either side of the Aravis range as you descend from the Trou and before you turn into Come de Paccaly.

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The GPS track and description are the property of the author.