 At the time of its construction, it was the longest single-arch span in the world; today, it is no longer used for rail transport and was replaced by a modern structure in 1991.It is often confused with the D. Luís Bridge, which was built nine years later and is located to the west, but resembles the structure, albeit with two decks.In 1875, the Royal Portuguese Railway Company announced a competition for a bridge to carry the Lisbon to Porto railway across the river Douro.