There are few free attractions in Porto, Portugal. One of them, and the most popular is the Dom Luís I Bridge in the Ribeira area.It connects Porto and Vila Nova de Gaia spanning the Douro River. The bridge was built by a disciple of Gustave Eiffel, Théophile Seyrig.At the time of its completion in 1886, the bridge was the longest iron arch in the world.The two deck bridge accommodates the metro on the upper level and cars on the lower level. Pedestrians can walk in both levels. Walking in the upper deck gives pedestrians a spectacular view.