Claim: Lisbon's status as a capital has never been officially confirmed in writing.

Lisbon -LRB- -LSB- ˈlɪzbən -RSB- Lisboa , -LSB- liʒˈβoɐ -RSB- -RRB- is the capital and the largest city of Portugal , with a population of 552,700 within its administrative limits in an area of 100.05 km ² . Its urban area extends beyond the city 's administrative limits with a population of around 2.7 million people , being the 11th-most populous urban area in the European Union . About 2.8 million people live in the Lisbon Metropolitan Area -LRB- which represents approximately 27 % of the country 's population -RRB- . It is continental Europe 's westernmost capital city and the only one along the Atlantic coast . Lisbon lies in the western Iberian Peninsula on the Atlantic Ocean and the River Tagus . The westernmost areas of its metro area is the westernmost point of Continental Europe .   Lisbon is recognised as a global city because of its importance in finance , commerce , media , entertainment , arts , international trade , education and tourism . It is one of the major economic centres on the continent , with a growing financial sector and one of the largest container ports on Europe 's Atlantic coast . Humberto Delgado Airport serves over 20 million passengers annually , as of 2015 , and the motorway network and the high-speed rail system of Alfa Pendular link the main cities of Portugal . The city is the 7th-most-visited city in Southern Europe , after Istanbul , Rome , Barcelona , Madrid , Athens and Milan , with 1,740,000 tourists in 2009 . The Lisbon region contributes with a higher GDP PPP per capita than any other region in Portugal . It 's GDP amounts to 96.3 billion USD and thus $ 32,434 per capita , 40 % higher than the average European Union 's GDP per capita . The city occupies 32nd place of highest gross earnings in the world . Most of the headquarters of multinationals in the country are located in the Lisbon area . It is also the political centre of the country , as its seat of Government and residence of the Head of State .   Lisbon is one of the oldest cities in the world , and the oldest in Western Europe , predating other modern European capitals such as London , Paris and Rome by centuries . Julius Caesar made it a municipium called Felicitas Julia , adding to the name Olissipo . Ruled by a series of Germanic tribes from the 5th century , it was captured by the Moors in the 8th century . In 1147 , the Crusaders under Afonso Henriques reconquered the city and since then it has been a major political , economic and cultural centre of Portugal . Unlike most capital cities , Lisbon 's status as the capital of Portugal has never been granted or confirmed officially -- by statute or in written form . Its position as the capital has formed through constitutional convention , making its position as de facto capital a part of the Constitution of Portugal .   Lisbon enjoys a Mediterranean climate . It has one of the warmest winters of any metropolis in Europe , with average temperatures 15 ° C during the day and 8 ° C at night from December to February . The typical summer season lasts about four months , from June to September , although also in April temperatures sometimes reach around 25 ° C.