Upper Danube Valley

Between Tuttlingen and Sigmaringen the Danube, still small here, runs through a canyon of white Jurassic limestone with crags and towers standing above the meadows, and castles on many of them. At the Donauversickerung near Immendingen, the riverbed is fissured and much or all of the water sinks into the rock; in dry periods the surface flow stops entirely for weeks. The water reappears about twelve kilometres south at the Aachtopf, which drains to Lake Constance and so to the Rhine, meaning part of the young Danube ends up in the North Sea rather than the Black Sea. Beuron abbey sits in the valley.

What you actually see

• The sinking river - a Danube bed that goes dry in low water.
• The Aachtopf link - water reappearing on the Rhine side of the divide.
• The limestone crags - white towers above meadows with castles on them.
• Beuron abbey - a Benedictine house in the middle of the valley.

When to go

April to October; the sinking is most complete in late summer and autumn dry spells, when the bed can be walked. Spring high water hides the effect entirely.

Honest expectations

The dry riverbed is a seasonal phenomenon and absent in wet periods. Public transport in the valley is limited. Castles are mostly private or ruined.

Nearby

Sigmaringen lies downstream; the Danube's source is west.