Lively, commercial Oporto is the second largest city in Portugal after Lisbon. Also called Porto for short, the word easily brings to mind the city's most famous product - port wine. Oporto's strategic location on the north bank of the Douro River has accounted for the town's importance since ancient times. The Romans built a fort here where their trading route crossed the Douro, and the Moors brought their own culture to the area. Oporto profited from provisioning crusaders en route to the Holy Land and enjoyed the riches from Portuguese maritime discoveries during the 15th and 16th centuries. Later, port wine trade with Britain compensated for the loss of the spice trade and the end of gold and gem shipments from Brazil. In the 19th century, the city went through a period of new prosperity with the rise of industries. In its wake followed the building of workers' quarters and opulent residences. Since the declaration of Oporto as a World Heritage Site by UNESCO, the city aims to build up a cultural reference that will provide it with a new image, based on deep historical roots. Among the attractions that make Oporto such an interesting place are its graceful bridges spanning the Douro River, a picturesque riverfront quarter and, most notable, its world-famous port wine lodges. Although Oporto is a bustling centre and home to many different businesses, the source of its greatest fame is the rich, sweet fortified red wine we know as port.