Danube conservation and touristic development of the Danube region. In medieval Regensburg, with its maintained old town, stone bridge and cathedral, the Route of Emperors and Kings begins. It continues to Engelhartszell, with the only Trappist monastery in Austria. Further highlight-stops along the Danube include the "Schlögener Schlinge", the city of Linz, which was European Capital of Culture in 2009 with its contemporary art richness, the Melk Abbey, the university city of Krems and the cosmopolitan city of Vienna. Before the Route of Emperors and Kings ends, you pass Bratislava and Budapest, the latter which was seen as the twin town
Danube the Rhine. The European Water Divide applies only for those waters that pass beyond this point, and only during the days of the year when the Danube carries enough water to survive the sink holes in the Donauversickerung. Since such large volumes of underground water erode much of the surrounding limestone, it is estimated that the Danube upper course will one day disappear entirely in favor of the Rhine, an event called stream capturing. The hydrological parameters of Danube are regularly monitored in Croatia at Batina, Dalj, Vukovar and Ilok. The Danube basin was the site of some of the