The Asseburg is a ruined hill castle on the narrow, southern crest of the Asse ridge in the Harz Mountains of Germany, not far from Wolfenbüttel. The castle was built around 1218 by Gunzelin of Wolfenbüttel and other nobles as a so-called Ganerbenburg, or castle managed and occupied by more than one family or branch. Based on its dimensions, this elongated fortification was the largest hill castle in North Germany and was considered impregnable. In 1492 it fell into ruins when it was abandoned and set on fire by its garrison during the course of a feud.