© All Rights Reserved The 1876 Dona Maria Pia bridge in Porto. Designed by Gustave Eiffel, the bridge is the only one of the six bridges spanning the Douro that is not usedRelated images Terraced Fields in the Douro Valley Igreja da Venerável Ordem Terceira de São Francisco Porto - Bishop's Palace and Luis I Bridge Cafe behind the Ribeira - Porto Cnetral Porto Buildings Ornate Facade - Porto