The Alster is a 53 km long right tributary of the river Elbe in Northern Germany. It has its source near Henstedt-Ulzburg in the village of Kisdorferwohld in Schleswig-Holstein, approximately 25km north of Hamburg. The Alster flows roughly southwards and reaches the Elbe in Hamburg, which was founded on its shore. In the centre of Hamburg the Alster has been dammed since 1190, originally to power a watermill. In 1235 a further dam was built for a second mill, which changed the form of the river… (More on Alster)