Barcelona is the capital and the most populous city of Catalonia and the second largest city in Spain, after Madrid, with a population of 1,621,537 within its administrative limits on a land area of 101.4 km2 (39 sq mi). The urban area of Barcelona extends beyond the administrative city limits with a population of over 4,200,000 on an area of 803 km2 (310 sq mi), being the sixth-most populous urban area in the European Union after Paris, London, Ruhr area, Madrid and Milan. About five million people live in the Barcelona metropolitan area. It is also Europe’s largest metropolis on the Mediterranean coast. It is the main component of a union of adjacent cities and municipalities named the Àrea Metropolitana de Barcelona (AMB) with a population of 3,186,461 in an area of 636 km² (density 5.010 hab/km²). It is located on the Mediterranean coast between the mouths of the rivers Llobregat and Besòs and is bounded to the west by the Serra de Collserola ridge (512 m/1,680 ft).