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
Ethnic groups in Europe Europe has been nearly equivalent to Christian culture, The Christian culture was the predominant force in western civilization, guiding the course of philosophy, art, and science. The notion of "Europe" and the "Western World" has been intimately connected with the concept of "Christianity and Christendom" many even attribute Christianity for being the link that created a unified European identity. Christianity is still the largest religion in Europe; according to a 2011 survey, 76.2% of Europeans considered themselves Christians. Also according to a study on Religiosity in the European Union in 2012, by Eurobarometer, Christianity is the largest religion in the