|Locale||Between Sucidava (present-day Corabia, Romania) and Oescus (modern Gigen, Bulgaria)|
|Total length||2,437 m (7,995 ft)|
|Width||5.7 m (19 ft)|
|Height||10 m (33 ft)|
|Construction end||328 AD|
|Opened||July 5, 328 AD|
Constantine's Bridge on the map
Constantine's Bridge (Bulgarian: ?, Konstantinov most; Romanian: Podul lui Constantin cel Mare) was a Roman bridge over the Danube in order to reconquer Dacia. It was completed or rebuilt in 328 AD and remained in use for no more than four decades.
It was officially opened on 5 July, 328 in the presence of the emperor Constantine the Great. With an overall length of 2437 m, 1137 m of which spanned the Danube's riverbed, Constantine's Bridge is considered the longest ancient river bridge and one of the longest of all time.
It was a construction with masonry piers and wooden arch bridge and with wooden superstructure. It was constructed between Sucidava (present-day Corabia, Olt County, Romania) and Oescus (modern Gigen, Pleven Province, Bulgaria), by Constantine the Great. The bridge was apparently used until the mid-4th century, the main reason for this assumption being that Valens had to cross the Danube using a bridge of boats at Constantiana Daphne during his campaign against the Goths in 367.
While Luigi Ferdinando Marsigli attempted to locate the bridge in the 17th century and Alexandru Popovici and Cezar Bolliac worked in the 19th, the first real scientific discoveries were performed by Grigore Tocilescu and Pamfil Polonic in 1902. In 1934 Dumitru Tudor published the first complete work regarding the bridge, and the last systematic approach on the north bank of the Danube was performed in 1968 by Octavian Toropu.