 It finally declined after the total change of the local hydrography in 589, following the catastrophic flood documented by Paul the Deacon, and Adria became a fief of the archdiocese of Ravenna.After a period as an independent commune, it was a possession of the Este of Ferrara and, in the 16th century, of the Republic of Venice.At that time Adria was a small village surrounded by malaria-plagued marshes.