In reply to iusedtoclimb:
Just shy of a 100 miles (144km) is the Échapée Belle near Grenoble -
http://www.lechappeebelledonne.com/
Also around Grenoble is the UT4M which is just over 100 miles -
http://ut4m.fr/en/
I've not done either of them but they're both on my list - I've two 86km races planned this year, will step up to 100 miler next year (that's the plan although out with calf injury at the moment).