The River Danube is the historical artery of eastern Europe, navigable from southern Germany to the Black Sea. The Danube Navigation Museum centres on vessels moored on the south bank of the river, between the Steinerne and Eiserne bridges (the Stone Bridge and the Iron Bridge). A ticket office is at Thundorferstraße 6. Displays and models show the history of river transport from prehistoric times to the present inside the Hungarian paddle-steamer Érsekcsanád. This vessel was built in Regensburg in 1923 under the name Ruthof and was rescued from scrapping in 1979 by the museum association, which was set up for the purpose. Moored beside it is Freudenau, a diesel tug commissioned by the Austrian shipping company DDSG in 1942 to tow vessels along the river. The association also looks after other objects in the city, including the cargo barge Helga built in 1955, the winch that pulled vessels upstream through the Stone Bridge, a hand-operated crane, an electric crane of 1912 and a steam boiler.