"How many mosques are there in Athens? It seems that Greeks prefer to prevent the construction of mosques in areas of need . What is worse , converting unused mosques into churches or preventing mosques being built in areas of large Moslem populations?"
i DEFY YOU TO SHOW EVEN ONE Mosque converted to a church in Greece. Such an act goes against the fundamentals of the Orthodox faith and would never be consecrated by any priest.
Athens has an old Mosque in the center which is unused. A new one is being built to serve the large immigrant community which came in the 90s and later.
In Greece as a whole there a plenty of Mosques to serve the 150 000 Moslem citizens, mostly in the northern towns of Komotini and Xanthi and surrounding areas.