The Alcántara Bridge is a Roman arch bridge located in Spain, spanning the Tagus River. Built in the early 2nd century AD during the reign of Emperor Trajan, it was designed to facilitate trade and military movement across the river. The bridge is notable for its impressive length of 194 meters and its height of 28 meters. Constructed from local granite, the Alcántara Bridge features a single large arch, which is a hallmark of Roman engineering. It has survived the test of time and remains one of the best-preserved Roman bridges in the world, showcasing the advanced construction techniques of the era.