TOMBLAINE, France — The Tour de France left the flats of northern France on Saturday for three days of up-and-down riding in the Vosges mountains.

The 161-kilometer (100-mile) Stage 8 from Tomblaine to the Gerardmer La Mauselaine ski resort features a short but steep uphill finish that will test the legs of overall leader Vincenzo Nibali and his main challengers for the yellow jersey.

The Italian holds a two-second lead over Astana teammate Jakob Fuglsang. He is also two minutes, 37 seconds clear of two-time Tour winner Alberto Contador, the rider considered his main rival now that defending champion Chris Froome is out of the race.

Swiss rider Mathias Frank, the leader of the IAM Cycling team, did not start the eighth stage after fracturing his left femur in a crash in the last kilometer (half-mile) of Friday's race.

Frank, runner-up in the Tour de Suisse last month and the Criterium International in March, underwent surgery in Geneva on Saturday.

The toughest rides in the Vosges will come Monday when cyclists face seven ascents, including a tough uphill finish up to the storied ski resort La Planche des Belles Filles.