The Aller has a total length of 260 kilometers. The source is located near Seehausen (Eggenstedt in the district of Börde in Saxony-Anhalt) and flows into the Weser a few kilometers west of Verden city center.
It is the largest tributary of the Weser and also the largest river in northern Germany that does not flow into the sea. In the 1960s, the Aller was partially straightened, widened and equipped with dykes for flood protection.
