The banks of the Douro are linked by several remarkable bridges. Among them one must mention the Maria Pia railway bridge, built by Gustave Eiffel, which is the most elegant with its single arch with a 350m span ; the D Luis I road bridge, built in 1886, which is the symbol of Porto and which formed part of the world heritage and the d'Arrabida road bridge, opened in 1963, which crosses the Douro in a single concrete arch of around 270m.