The Saint Nicholas Chapel is one of the few remaining parts of the Valkhof, a citadel built by Charlemagne, in Nijmegen in the Netherlands. The origins of the chapel itself are pretty vague. It was possibly founded by Theophanu, abbess of Essen, whose grandmother and namesake was the Empress Theophanu who died at the Valkhof in Nijmegen. It was most likely built around 1000/1050. Empress Theophanu was buried in Cologne.
During the course of her life, Theophanu probably visited the Valkhof several times though this was most likely before the building of the chapel.