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).
Some remaining fragments of the Roman walls have been incorporated into the cathedral.
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.
The definitive metre bar, manufactured from platinum, was presented to the French legislative assembly on 22 June 1799.
Particularly renowned are the architectural works of Antoni Gaudí and Lluís Domènech i Montaner, which have been designated UNESCO World Heritage Sites.