The Maria Pia bridge (Ponte Maria Pia), commonly known as Ponte Dona Maria, is a railway bridge built in 1877 by Gustave Eiffel in Porto, Portugal. Built of wrought iron, its two-hinged crescent arch used to carry the railway to Lisbon for 353 metres (1,158 ft) across the River Douro at a height of 60 m (200 ft) above the river. When constructed it was the longest single-arch span in the world.