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
Metropolitan City of Naples capital city. Due to the presence of Vesuvius and Phlegraean Fields, the city is vulnerable to seismic and volcanic activity. The city is 96th out of 110 Italian provinces and metropolitan cities by landmass, with an area (1,171 km² including islands) that is smaller than the core "comune" of Rome (1,287 km²). Naples is nevertheless Italy's 3rd largest city by population, making it one of the most densely populated areas in Europe; the metropolitan region also includes the municipality of Casavatore, the highest-density municipality in Italy (at 12,000 inhabitants/km²). While it contains more than half of Campania's population, it only