Eresburg may have been the site of the Irminsul, a sort of pillar or tree, and one of the chief pagan religious sites of the Saxons. The wording of the Royal Frankish Annals in 772 suggests that the Irminsul might have been located either at the Eresburg itself or in the near vicinity. The Annales Petaviani states: "He conquered the Eresburg and found the place which is called Ermensul, and set these places on fire."
Eresburg may have been a site of pagan religious significance for the Saxons, possibly housing the Irminsul, a pillar or tree of great importance. The Annales Petaviani confirms this by stating that the ruler conquered Eresburg and found the place called Ermensul, which was likely the location of the Irminsul.