The Puente Romano (Spanish for Roman Bridge) is a Roman bridge over the Guadiana River at Mérida in southwest Spain.
It is the world’s longest (in terms of distance) surviving bridge from ancient times, having once featured an estimated overall length of 755 m with 62 spans. Today, there are 60 spans (three of which are buried on the southern bank) on a length of 721 m between the abutments. Including the approaches, the structure totals 790 m. It is still in use, but was pedestrianized in 1991 as road traffic was redirected to use the nearby Lusitania Bridge.
The original bridge was built in two sections with a huge cutwater that stretched upstream to stem the force of the current. A big flood destroyed the cutwater in the 17th century. Five new arches were built to join the two sections of the bridge, making it one long structure. An access ramp links the bridge to the remains of the cutwater, which is now a park.
Annexed to the bridge is the Alcazaba of Mérida, a Moorish fortification built in 835. Close to the remains of the Acueducto de los Milagros, there exists another Roman bridge at Mérida, the much smaller Puente de Albarregas.
According to Wikipedia