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
Islam in Europe Islam in Europe Islam is the second-largest (after Christianity) and fastest-growing religion in Europe. Although the majority of Muslim communities in Europe formed recently, there are centuries-old Muslim societies in the Balkans. Islam entered southern Europe through the invading "Moors" of North Africa in the 8th–10th centuries; Muslim political entities existed firmly in what is today Spain, Portugal, South Italy and Malta for several centuries. The Muslim community in these territories was converted or expelled by the end of the 15th century (see "Reconquista"). Islam expanded into the Caucasus through the Muslim conquest of Persia in the 7th century. The