Porto also known as Oporto in English, is the second-largest city in Portugal, after Lisbon. The urban area of Porto, which extends beyond the administrative limits of the city, has a population of 1.4 million. Located along the Douroriverestuary in Northern Portugal, Porto is one of the oldest European centres, and its historical core was proclaimed a WorldHeritageSite by UNESCO in 1996. The western part of its urban area extends to the coastline of the AtlanticOcean. Its settlement dates back many centuries, when it was an outpost of the Roman Empire. Its combined Celtic-Latin name, Portus Cale, has been referred to as the origin of the name "Portugal", based on transliteration and oral evolution from Latin. In Portuguese, the name of the city is spelled with a definitearticle ("o Porto"; English: the port). Consequently, its English name evolved from a misinterpretation of the oral pronunciation and referred to as Oporto in modern literature and by many speakers. One of Portugal's internationally famous exports, port wine, is named for Porto, since the metropolitan area, and in particular the caves of VilaNova de Gaia, were responsible for the production and export of the fortified wine.