Numerous tarns in the Northern Black Forest are evidence of ice age glacial formations, The best-known is the Mummelsee on the Hornisgrinde. Other tarns are the Ellbachsee, Herrenwieser See, Huzenbacher See, Sankenbachsee, Schurmsee and the Wildsee near Ruhestein. Many of them were also impounded in order to supply excess water for timber rafting which was common until the 19th century. Other former tarns have silted up.