Vila Nova de Gaia or simply Gaia, is a city and a municipality in Porto District in Norte Region, Portugal. It is located south of the city of Porto on the other side of the Douro River. Gaia along with Porto and 12 other municipalities make up the commonly designated Porto Metropolitan Area. The city contains many cellars (locally known as "caves") where port wine is stored and aged. These cellars have become a major tourist attraction.