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
Transportation in New York City state of New York, which runs all of the city's subways and buses and two of its three commuter rail networks. Ridership in the city increased 36% to 2.2 billion annual riders from 1995 to 2005, far outpacing population growth. Average weekday subway ridership was 5.076 million in September 2006, while combined subway and bus ridership on an average weekday that month was 7.61 million. The New York City Subway is the largest subway system in the world when measured by number of stations (), and the seventh-largest when measured by annual ridership (1.76 billion passenger trips in 2015). It