Stahleck Castle, 12th-century castle in Bacharach, Germany

Stahleck Castle stands on a crag about 160 metres above sea level on the left bank of the Rhine at the mouth of the Steeg valley. Its tall cylindrical keep of dark grey stone carries a steep conical roof; to its left a lower square tower with a pointed roof and a small turret, to the right a larger building with a half-timbered upper storey. Stone walls with small windows link the buildings, and rows of vines grow on the slope below.

Stahleck was probably founded around the turn of the 12th century by the Archbishops of Cologne as a southern outpost of their archbishopric, and a Gozwin von Stalecke is first documented as its feudal holder in 1120/21. From 1142 it was the seat of the Counts Palatine by Rhine, and Bacharach's wine trade made it a toll castle. Besieged and taken eight times in the Thirty Years' War, it was blown up by French troops in 1689 and stood as a ruin until the Rhineland Association for Monument Conservation bought it in 1909 and rebuilt it from 1925 as a youth hostel.

The castle displays medieval defense design with its rare water-filled moat and commands the landscape from its position above the river valley. Visitors can observe how the construction adapts to the steep hillside and follows the defensive lines.

The castle has housed a youth hostel since 1925, so interior visits are not possible; guests sleep in the rebuilt rooms. Day visitors can still reach the large terrace, which looks over the Upper Middle Rhine Valley and the Lorelei valley. The site stands on the left bank at the mouth of the Steeg valley, about 50 km south of Koblenz.

The name combines Middle High German stahel (steel) and ecke (crag), meaning "impregnable castle on a crag". Its water-filled partial moat is a rarity in Germany. In 1193/94 Agnes of Hohenstaufen secretly married Henry the Elder of Brunswick here while her father was away, an event known as the Stahleck Marriage.