Founded as a Roman city, Barcelona is the capital and largest city of Catalonia, as well as the second most populous municipality of Spain. With a population of 1.6 million within city limits, its urban area extends to numerous neighboring municipalities within the Province of Barcelona and is home to around 4.8 million people, making it the sixth most populous urban area in the European Union after Paris, London, Madrid, the Ruhr area and Milan.  (Sited from wikipedia.) I did a little comparison from the data on Wikipedia. Barcelona is the most densely populated urban area among Atlanta, Shanghai and New York. Shanghai and New York are similar in terms of urban density, but outside of the city limit, Shanghai still has the high density while…