Porto is the second largest city in Portugal, located at the mouth of the Douro River. It is famous for its ancient cultural heritage and charming riverside landscape. The historic district in the city is listed as a World Heritage Site by UNESCO. The ancient churches, narrow alleys and colorful buildings interweave into a unique style. Porto is famous for its port wine. Visitors can visit the winery and taste the unique wine. There are both romantic riverside walks and vibrant markets and cafes here, attracting countless tourists.