From Yahoo Sports: Cyclists ride bikes on the ski slopes in the alpine resort of Villars, Switzerland, during the New Year's eve mountain bike snow race, Monday, Dec. 31, 2007. Nearly 100 cyclists rode the 5 km track on snow. (AP Photo/Keystone/Laurent Gillieron)
But don't worry, this type of fun can be had stateside as well. According to an article on www.cyclingnews.com than ran on January 3, 2008:
Winter downhilling returns to Pennsylvania
While many riders in Pennsylvania will be busy working up the nerve to head out and ride in the winter cold, a few brave souls will be racing the eighth annual winter downhill race at Blue Mountain Ski Area in Palmerton, Pennsylvania, on January 5 at 10:30 am local time. Four racers per heat will compete mountain cross style reaching speeds of up to 50mph.