A first settlement, probably restricted to a tiny islet in the Oker river, was founded in the tenth century. It was mentioned in 1118 as "Wulferisbuttle", when the Saxon count Widekind of Wolfenbüttel had a water castle erected on the important trade route from Brunswick to Halberstadt and Leipzig. Destroyed by Henry the Lion in 1191, and again by his great-grandson Duke Albert I of Brunswick-Lüneburg in 1255, the fortress and town, as well as nearby Asseburg Castle, were seized in 1258 by Albert I from the House of Asseburg, the descendants of Widekind. The castle was rebuilt by the Welf duke Henry I of Brunswick from 1283 onwards.