While the Chamonix Valley itself is renowned for its ice falls, with more than 200 routes in 10 locations for all levels and skills, if one looks further afield, there is a fantastic array of venues for this sublime sport.
Just through into Italy is Cogne, a venue that offers a fantastic array of routes of all standards with easy access. An then their is the Trient valley with an array of diffivult multi pitch routes.
The ice falls at altitude normally start to form around December. The lower falls start forming from January onwards with the best ice fall climbing months being between January and February.