The Grand Tour of the Portes du Soleil (Gateways to the Sun) uses ski lifts and mountain trails to traverse a gloriously beautiful part of the European Alps on the border between France and Switzerland to the south of Geneva. At 80km it's a bit of a marathon but there is much more downhill riding that uphill thanks to the ski lifts.
There is some great intermediate singletrack but it's mainly on mountain trails and roads, especially on the Swiss side of the border.
Starting in Morzine you take the Super-Morzine lift and go in the general direction of Avoriaz, Chatel, Morgins, Champoussin, Champery, Les Crosets, Les Lindarets, Montriond and back to Morzine. The signage is not good for the first 30km which is where my phone died along with the GPS trace I was following. Fortunately the signage is better for the rest of the circuit. You can follow my partial GPS trace on singletracks or buy the whole circuit and lots more here: http://www.vtopo.fr/vtopo-vtt-portes-du-soleil-integral.html
Along the way you will pass dozens of ski lifts, hikers and mountain bikers and some amazing downhill singletrack. And all around are alpine vistas to die for along with towns, villages and wonderful mountain restaurants, bars and cafes! But don't delay - the circuit takes around eight hours.