The Alconétar bridge on the river Tagus in Spain is one of the oldest stone segmental arch bridges in the world, predating other examples such as the Zhaozhou Bridge in China and Ponte Vecchio in Europe (both of which are still in use today). However the Ponte San Lorenzo is another smaller Roman segmental arch bridge that predates this one by more than 200 years. The bridge is Roman and its construction is attributed by some to Trajan's architect Apollodorus of Damascus, who also built the timber-arched Trajan's Bridge in the early 2nd century.
The bridge was relocated from its original position when the Alcántara reservoir was created in the province of Cáceres, Extremadura, Spain . Two original segmental arches were preserved, of 6.7m and 7.2m span, and a span-to-rise ratio of between 4 and 5, as were segmental arches from a later date . There is evidence from the position of piers that segmental spans up to 10m may have been present in the original construction.