Barcelona (Catalan pronunciation: [bəɾsəˈlonə], Spanish: [barθeˈlona]) is the capital and the most populous city of the Autonomous Community 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 a area of 803 km2 (310 sq mi), it is the sixth-most populous urban area in the European Union after Paris, London, Ruhr area, Madrid and Milan. About 5 million people live in the Barcelona metropolitan area. It is also Europe's largest metropolis on the Mediterranean coast. The main part of a union of adjacent cities and municipalities named 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).
Founded as a Roman city, Barcelona became the capital of the Counts of Barcelona. After merging with the Kingdom of Aragon, it became one of the most important cities of the Crown of Aragon. Besieged several times during its history, Barcelona is today an important cultural centre and a major tourist destination and has a rich cultural heritage. Particularly renowned are architectural works of Antoni Gaudí and Lluís Domènech i Montaner that have been designated UNESCO World Heritage Sites. The city is well known in recent times for the 1992 Summer Olympics. The headquarters of the Union for the Mediterranean are located in Barcelona.
As the capital of Catalonia, Barcelona houses the seat of the Catalan government, known as the Generalitat de Catalunya; of particular note are the executive branch, the parliament, and the Supreme Court of Catalonia. The city is also the capital of the Province of Barcelona and the Barcelonès comarca (shire).
Barcelona enjoys a Mediterranean climate. The summer's season lasts about 6 months, from May to October, although also in November and April sometimes there are temperatures above 20 °C (68.0 °F). Winters are mild, with average temperatures over 14.5 °C (58.1 °F) during the day and 5.5 °C (41.9 °F) at night in the period December to March.