Short answers, pulled from the story.
Donaueschingen is a town in the Black Forest in the southwest of the federal state of Baden-Württemberg, within the Schwarzwald-Baar Kreis district. It sits about 13 km south of Villingen-Schwenningen and about 30 km north of the Swiss town of Schaffhausen.
Donaueschingen is recognized as the source of the Danube because the Brigach and Breg rivers, the two source tributaries of the Danube, meet just outside the town. An enclosed karst spring in the park of Donaueschingen Palace, feeding a stream called the Donaubach, is also traditionally marked as the river's origin.
The Donaueschinger Musiktage is an annual festival for contemporary music founded in 1921, making it one of the world's oldest festivals for new music. It takes place every October and has hosted composers including Paul Hindemith, Arnold Schoenberg, Pierre Boulez, John Cage, and György Ligeti.
The U.S. Air Force operated a contingency hospital in Donaueschingen until the early 1990s. Its most active use came in 1989, when the United States offered the facility as temporary housing for refugees leaving East Germany for the West.
The Princes of Fürstenberg were the ruling family of Donaueschingen from the 18th century and made Schloss Donaueschingen their residence. Their control of the town traces to 1283, when Rudolph von Habsburg granted the principality of Baar and Donaueschingen to Heinrich von Fürstenberg, a grant that also included the right to brew beer and gave rise to the Fürstenberg Brewery.
The Fürstenberg Library in Donaueschingen holds early copies of five of Mozart's operas, which have been an important source for historically informed performances of 18th-century opera. The Fürstenberg family also owned Manuscript C of the Nibelungenlied until they sold it in 2001.