Lisbon metropolitan area
The Lisbon metropolitan area, centered in the Portuguese capital city of Lisbon, is the largest population concentration in Portugal. The population in 2011 was 2,821,876, of whom 547,733 (19.4%) live in the city of Lisbon. About 26.7% of the total population of Portugal lives in the Lisbon metropolitan area. The area of the Lisbon metropolitan area is 3,015.24 km, which is 3.3% of the total area of Portugal.
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.