Burg Arnstein, Medieval castle ruins in Arnstein, Germany

Burg Arnstein is a ruined hilltop castle on a 210-metre elevation between Sylda and Harkerode. Its most visible element is a tower-like Gothic hall building, originally four storeys high, alongside two Romanesque round towers and the curtain wall between them. Later additions include the Mittelhaus and remains of the castle church and kitchen house.

Walther II von Streußlingen was the first documented owner in the 12th century and took the name Walther von Arnstein for his family line. His descendants expanded and modified the fortress across multiple generations to meet changing needs.

The castle's name comes from the Swabian lords of Steußlingen, whose Walther II called himself after the castle in 1156. From the 19th century the Knigge family opened the ruin to visitors, and since 1992 a local heritage association has secured the masonry. The site also served as a film set, including for the 1975 Till Eulenspiegel adaptation.

The ruins are accessible via multiple walking paths starting from the villages of Sylda and Harkerode, each offering different lengths and perspectives. Shorter routes work well for quick visits, while longer trails give you time to explore the entire site.

In 1530 and 1563, the castle underwent major restructuring with residential and church areas elevated and completely rebuilt from the ground up. These reconstructions remain visible in the structure today, showing how the fortress adapted to the needs of its era.