The great plague of 1650–1654 halved the city's population.
In the 18th century, a fortress was built at Montjuïc that overlooked the harbour.
Another common abbreviation is 'BCN', which is also the IATA airport code of the Barcelona-El Prat Airport.
The city is also referred to as the Ciutat Comtal in Catalan, and Ciudad Condal in Spanish, owing to its past as the seat of the Count of Barcelona.
In 1794, this fortress was used by the French astronomer Pierre François André Méchain for observations relating to a survey stretching to Dunkirk that provided the official basis of the measurement of a metre.
The definitive metre bar, manufactured from platinum, was presented to the French legislative assembly on 22 June 1799.
The city was conquered by the Visigoths in the early 5th century, becoming for a few years the capital of all Hispania.However, this name refers only to FC Barcelona, the football club.The common abbreviated form used by locals is Barna.Madrid became the centre of political power whilst the colonisation of the Americas reduced the financial importance (at least in relative terms) of Mediterranean trade.Barcelona was a centre of Catalan separatism, including the Catalan Revolt (1640–52) against Philip IV of Spain.Important Roman vestiges are displayed in Plaça del Rei underground, as a part of the Barcelona City History Museum MUHBA; the typically Roman grid plan is still visible today in the layout of the historical centre, the Barri Gòtic (Gothic Quarter).