The Mummelsee is a small but famously moody cirque lake set at 1036 metres on the eastern flank of the Hornisgrinde. It is the most legendary of the Black Forest lakes — folklore made it the home of water sprites — and as a result the most visited. A hotel-restaurant stands on the shore and rowing boats can be hired in summer.
The setting is the draw: a perfectly round black-water lake ringed by spruce, with the moorland of the Hornisgrinde rising behind it. From Freudenstadt the drive north along the Schwarzwald Hochstrasse takes about an hour and is itself one of the great scenic routes in Germany. Aim for a weekday or early morning to avoid the bus crowds.