Ilburg, Medieval castle ruin on Großer Burgberg in Harztor, Germany.

Ilburg is a castle ruin perched on Großer Burgberg in Harztor at approximately 300 meters elevation. The site preserves wall sections, foundation remains, and a restored well from the medieval structure.

According to local tradition, Elgerus de Bilstein built the castle around 1150 and later called himself Count of Ilfeld. His successor Adelger von Ilfeld married Lutrude von Hohnstein around 1162, founding the Hohnstein comital dynasty. Around 1180 Elger II moved his residence to neighbouring Hohnstein Castle, and the smaller Ilburg was abandoned around 1189. Its stones were later reused in the building of Ilfeld Monastery, founded by the counts of Hohnstein.

The name Ilburg survives in local tradition, which credits Elgerus de Bilstein with building the castle around 1150; he then called himself Count of Ilfeld. His successor Adelger married Lutrude von Hohnstein around 1162, and the couple founded the Hohnstein comital dynasty. The abandoned castle's stones were later reused to build Ilfeld Monastery.

The site is accessible throughout the year, but the terrain features uneven paths covered with vegetation that require sturdy hiking footwear. Weather conditions can make the routes slippery, so extra caution is wise.

The castle was probably built around 1150 by Elgerus de Bilstein, who then called himself Count of Ilfeld; his successor Adelger married Lutrude von Hohnstein around 1162, founding the Hohnstein comital dynasty. Around 1189 the abandoned castle's stones were reused to build Ilfeld Monastery.