This is a beautiful two day hike from near the town of Sixt Fer à Cheval (near Morzine and not far from Chamonix) best suited for strong hikers.
The first night was a relatively short ascent with 1050m of height gain to a mountain hut above Sixt at 1950m altitude where we enjoyed a lovely meal and warm beds.
The second day is the longest and started with breakfast at the hut, and was 1140m of height gain, with large amounts of ridge traversing and beautiful vistas across the Cirque des Fonts. We had lunch on Mt Buet and then started our return journey with 2200m of height loss. The last day could be turned into two days to be less exhausting, staying in an beautiful refuge in the Cirque des Fonts turning this a three day hike. This is a lovely trek in the autumn when the leaves are turning colors.
This year we went in mid-September and the scenery and tree foliage was amazing with bright blue crystal clear skies, and the route was not crowded. There were a few late blooming alpine flowers on view, and we also managed to see a family of ibex. There is a bit of an airy scramble using chains to ascend the ridge-line to the summit of Mt Buet, which is 3096m (sometimes also quoted as 3098, 3099 or 3100m) in altitude. The route also gave us an opportunity to view first-hand the effects of global warming, as several of the nearby smaller glaciers marked on the map were already gone or disappearing.
Descent was by a completely different route which loops back to the car park, and has many long downhills, and chances to view ibex perched in the rocks as we descended Mt Buet. From the summit of Mt Buet there were beautiful views for 360 degrees.
This route is often done for acclimatisation before climbing Mont Blanc, as part of other multi-day tours in the region. It is easily enjoyed as a two to three day hike in its own right when done from this side of the mountain.
This is a really nice trekk to do. I do not say this because I am french, it is just that I love this part of the Alps. Some of my pictures and trekk : http://www.sports-sante.com/index.php/randonnee-dans-le-cirque-de-fer-a-cheval-a-sixt
Véro from Sports et Santé blog