The Schaalsee is the deepest lake in northern Germany, a long, dark, cold trough more than seventy metres down in its deepest part, gouged by a glacier and then filled with meltwater. The area around it is a UNESCO biosphere reserve, and it is one of the least spoiled landscapes in the north: lakes, reedbeds, meadows, beech forest and small villages with brick farmhouses and church towers.
The reason it is so undisturbed is political. For forty years the inner German border ran through the middle of the lake, with the western shore in the Federal Republic and the eastern in the GDR, and a strip of land on either side was off limits. Fences, watchtowers and patrols kept people out and nature in. When the border opened in 1989, the strip had become an accidental wildlife refuge, and it now forms part of the Green Belt, the chain of protected land that runs along the former frontier from the Baltic to Bohemia. White-tailed eagles nest here, cranes gather on the fields in autumn, and the reedbeds hold bitterns and otters.
On a bike the biosphere is a landscape for slow, curving riding. Roads run between hedges and fields, through villages and along the lake in places, with a rolling pattern that keeps things interesting. The tarmac is generally good, and traffic is light except on summer weekends, when the lake beaches fill up. Be alert for cyclists and farm vehicles, and for deer at dawn and dusk. Autumn is a spectacular time, with mist on the water, migrating geese and the beeches in colour.
There is not much in the way of services right at the water. Zarrentin, a few kilometres away, is a small town with a lake beach and a ruined monastery and has shops and cafés, and Wittenburg, about thirteen kilometres off, is the nearest place with a good range, including fuel. Plan fuel in advance. A visitor centre in the area explains the reserve and the history of the border, and it is worth a short stop if you have time. Bring a layer, because the wind off the lake can be cool even in July.