PETERWARDEIN (Hung. Petervarad, Serv. Petrovaradin)  , a royal free town and fortress of Hungary in the county of Syrmia, Croatia-Slavonia; situated on a promontory formed by a loop of the Danube, 62 m . N.W. of Belgrade by rail . Pop . (1900), 5019 . It is connected with Neusatz on the opposite hank by a bridge of boats, a railway bridge and a steam ferry . The fortifications consist of the upper fortress, on a lofty serpentine rock rising abruptly from the plain on three sides, and of the lower fortress at the northern base of the rock . The two fortresses can accommodate a garrison of ro,000 men . In the lower fortress is the town, with a military hospital, and an arsenal containing trophies captured from the Turks . Peterwardein, the " Gibraltar of Hungary," is believed to represent the Roman Acumincum, and received its present name from Peter the Hermit, who here in 1096 marshalled the levies of the first crusade . It was captured by the Turks in 1526 and retained by them for 16o years . In 1716 it witnessed a signal defeat inflicted on the Turks by Prince Eugene . During the revolutionary struggles of 1848–49 the fortress was held by the insurgents for a short time .