Barcelona ( /bɑrsɨˈloʊnə/, ) is the capital 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 between 4,200,000 and 4,500,000 within an area of 803 km2 (310 sq mi), being the sixth-most populous urban area in the European Union after Paris, London, the Ruhr, Madrid and Milan. About five million people live in the Barcelona metropolitan area. It is also the largest metropolis on the Mediterranean Sea. 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).
Founded as a Roman city, Barcelona became the capital of the County of Barcelona. After merging with the Kingdom of Aragon, Barcelona became one of the most important cities of the Crown of Aragon. Besieged several times during its history, Barcelona has a rich cultural heritage and is today an important cultural centre and a major tourist destination. Particularly renowned are the architectural works of Antoni Gaudí and Lluís Domènech i Montaner, which have been designated UNESCO World Heritage Sites. The headquarters of the Union for the Mediterranean is located in Barcelona. The city is known for hosting the 1992 Summer Olympics as well as world-class conferences and expositions and also many international sport tournaments.
Barcelona is today one of the world's leading tourist, economic, trade fair/exhibitions and cultural-sports centres, and its influence in commerce, education, entertainment, media, fashion, science, and the arts all contribute to its status as one of the world's major global cities. Indeed, it is a major cultural and economic centre in southwestern Europe (Iberian Peninsula), 26th in the world (after Moscow, before Dubai) and a growing financial centre (Diagonal Mar and Gran Via). It is the fourth economically powerful city by GDP in the European Union and 35th in the world with an output amounting to €177 billion. As of 2009 the city was ranked Europe's third and one of the world's most successful as a city brand. At the same time, the city was ranked Europe's fourth best city for business and fastest improving European city, with growth improved by 17% per year. Barcelona is the transport hub with one of Europe's principal ports, Barcelona international airport, which handles above 34 million passengers per year, extensive motorway network and also is a hub of high-speed rail, particularly that which is intended to link Spain with France and the rest of Europe as the second longest in the world.