The number three world destination on the rise is also seaside city. Porto, Portugal sits on Atlantic Coast. Its old town is a UNESCO World Heritage site. The Douro River flows by the city on its way to the sea. The Douro River Valley is known for its high-quality wine. Its most famous is port. Port wines are sweeter and higher in alcohol content than most wines. Above the Douro river is one of Porto’s most iconic sites. The Dom Luis bridge opened in 1886. A student of Gustave Eiffel -- of Eiffel Tower fame -- designed the bridge. The top level is for walkers; the lower level is for cars. The bridge provides beautiful views of the river and city.