The Blau is a 15 km long river in Baden-Württemberg, southern Germany, left tributary of the Danube. The source of the Blau is the karst spring Blautopf, in the town Blaubeuren, in the Swabian Alb. It flows east through Blaustein to the city of Ulm, where it flows into the Danube. A river is a large natural waterway. ... Baden-Württemberg is a federal state in southwestern Germany to the east of the Upper Rhine. ... The Danube bend at Visegrád is a popular destination of tourists The Danube (ancient Danuvius) is Europes second-longest river (after the Volga). ... Karst topography occurs when a landscape is marked by underground drainage patterns. ... Blaubeuren is a town near Ulm in Germany. ... A view on the Swabian Alb, with its typical hills and a juniper meadow The Albtrauf, which forms the western border of the Swabian Alb The Swabian Jura (German: Schwäbische Alb) is a plateau in Baden-Württemberg, Germany, extending 220 km from southwest to northeast and 40 to... Blaustein is a municipality in the Alb-Donau district, in Baden-Württemberg, Germany. ... Ulm is a city in the German Bundesland of Baden-Württemberg, situated on the river Danube, about 90 km south-east of Stuttgart and 140 km north-west of Munich. ... The Danube bend at Visegrád is a popular destination of tourists The Danube (ancient Danuvius) is Europes second-longest river (after the Volga). ...