Blau (Danube) in the context of "Blaubeuren"

A karst spring or karstic spring is a spring (exsurgence, outflow of groundwater) that is part of a karst hydrological system.

Ulm (German pronunciation: [ʊlm] ) is the sixth-largest city of the southwestern German state of Baden-Württemberg, and with around 129,000 inhabitants, it is Germany's 60th-largest city.

Ulm is located on the eastern edges of the Swabian Jura mountain range, on the upper course of the River Danube, at the confluence with the small Blau Stream, coming from the Blautopf in the west. The mouth of the Iller also falls within Ulm's city limits. The Danube forms the border with Bavaria, where Ulm's twin city Neu-Ulm lies. The city was part of Ulm until 1810, and Ulm and Neu-Ulm have a combined population of around 190,000. Ulm forms an urban district of its own (Stadtkreis Ulm), and is the administrative seat of the Alb-Donau-Kreis, the district that surrounds it on three sides, but which the city itself is not a part of. Ulm is the overall 11th-largest city on the river Danube, and the third-largest German Danubian city after Regensburg and Ingolstadt.

The Blautopf (German pronunciation: [ˈblaʊˌtɔpf], lit. 'Blue pot') is a spring that is considered the source of the river Blau in the karst landscape on the Swabian Jura's southern edge. It is located in Blaubeuren, Alb-Donau-Kreis, Baden-Württemberg, Germany (approximately 16 km (9.9 mi) west of Ulm).