Alt Eberstein, Medieval tower ruins in Baden-Baden, Germany.

Alt-Eberstein is a ruined spur castle on a 480-metre hill above Ebersteinburg, a district of Baden-Baden. Its oldest surviving element is the shield wall, 30 metres long and 14 metres high, built of porphyry conglomerate blocks. A square keep 18 metres tall was later added on top of the shield wall; the inner courtyard measured about 20 by 20 metres.

The site was founded around 1100 as a seat of the Counts of Eberstein and first appeared in written records in 1197. The fortress was abandoned over time and later served as a stone quarry for building local homes.

A legend painted in the Trinkhalle at Baden-Baden tells of a bishop of Strasbourg backed by the Counts of Eberstein against Emperor Otto I. The emperor besieged the castle for over a year, then invited the counts to a tournament at Speyer to seize it in their absence. His daughter warned the youngest count, and the counts returned in time to repel the attack; the emperor then gave her to Count Eberhard in marriage.

The ruins are accessible on foot via hiking trails or by car, with paths clearly marked along the way. Once there, information boards help explain the old structures and allow you to enjoy the views.

After the fortress was abandoned around 1573, it was stripped for stone for decades, with materials used to build homes in the surrounding area. This stone reuse is still visible in Baden-Baden buildings today if you look closely.