Coimbra is a city and a municipality in Portugal. The population at the 2011 census was 143,397, in an area of 319.40 square kilometres. The fourth-largest urban centre in Portugal, it is the largest city of the district of Coimbra, the Centro region and the Baixo Mondego subregion. About 460,000 people live in the Regiao de Coimbra, comprising 19 municipalities and extending into an area 4,336 square kilometres. Among the many archaeological structures dating back to the Roman era, when Coimbra was the settlement of Aeminium, are its well-preserved aqueduct and cryptoporticus. Similarly, buildings from the period when Coimbra was the capital of Portugal still remain. During the Late Middle Ages, with its decline as the political centre of the Kingdom of Portugal, Coimbra began to evolve into a major cultural centre.