Europe of population are Saint Petersburg, Madrid, Berlin and Rome, each having over 3 million residents. When considering the commuter belts or metropolitan areas, within the EU (for which comparable data is available) London covers the largest population, followed in order by Paris, Madrid, Barcelona, Berlin, the Ruhr area, Rome, Milan, Athens and Warsaw. "Europe" as a cultural concept is substantially derived from the shared heritage of the Roman Empire and its culture. The boundaries of Europe were historically understood as those of Christendom (or more specifically Latin Christendom), as established or defended throughout the medieval and early modern history of
Demographics of Europe For example, in the United Kingdom, the 2001 census revealed that over 70% of the population regarded themselves as "Christians" with only 15% professing to have no religion, though the wording of the question has been criticized as "misleading" by the British Humanist Association. The 2011 census showed a dramatic reduction to less than 60% of the population regarding themselves as "Christians". Despite its decline, Christianity is still the largest religion in Europe. According to a survey published in 2010, 76.2% of Europeans identified themselves as Christians. Catholics were the largest Christian group in Europe, accounting for more than 48%