Zaragoza is the capital and largest city of Aragon in Spain, and one of Spain's five largest cities, but it is one of the least known outside of Spain. Founded on the river Ebro during the Roman Empire as Cesaraugusta, Zaragoza now holds a large cultural and architectural heritage attesting to 2,000 years of affluence and importance. The city is best known for its Basilica del Pilar, built to venerate the apparition of the Virgin Mary to Saint James in very early Christian times, which became a major marker of cultural identity for Christian Spain. The city was again put on the global map by the 2008 Expo, which left it with a whole new modern part developed further for various purposes after the exhibition closed.