Lisbon
Lisbon (; , ) is the capital and the largest city of Portugal, with an estimated population of 505,526 within its administrative limits in an area of 100.05 km. Its urban area extends beyond the city's administrative limits with a population of around 2.8 million people, being the 11th-most populous urban area in the European Union. About 3 million people live in the Lisbon Metropolitan Area (which represents approximately 27% of the country's population). It is mainland 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 form the westernmost point of Continental Europe, which is known as Cabo da Roca, located in the Sintra Mountains.
National redoubt
Since the early 19th century to the World War II, Lisbon was considered the national redoubt of Portugal. Besides being the capital, the largest city and the major port of the country, Lisbon was considered the last defensible redoubt in case of an invasion of Portugal by a major power. During this period, successive systems of defense were implemented.