Rocher de la Mouche (Fly Rock) is located to the east of the hiking pass of l'Arc (Col de l'Arc) near the village of Lans-en-Vercors on Vercors Regional Natural Park in Isère department of France. The small opening has a measured span of 1.2 meter. The name comes from the fact that rock resembles to a fly (no overview of the whole rock on the photo below). The arch would be his trunk. IGN topographic map Top 25 number 3235 west Autrans (pleat E9).