The French website 5 Years Later has posted maps that illustrate the advance of Islam in France. I’ve taken the latest one from 2008 showing through shades of green the areas of implantation of the religion of peace and tolerance. The numbers on the map are those of the departments and have nothing to do with numbers of Muslims. The chart at the bottom runs from fewer than 5 to more than 30 mosques, prayer rooms or meeting houses. So we see that, in the southwest, department 33 has more than 30 while department 40 has fewer than 5.
For a complete list of all places of Islamic worship in France, click the link above. Even if you don’t know French you will find the listing impressive.
You will note also the inset in the upper left showing Paris (75) and its three surrounding suburbs. The name for that whole region is Ile-de-France, but someone has chosen to emend it to Êl-de-France.