A castle in the Apennines, in Italy, where, in the winter of 1077, the German emperor Henry IV waited for three days until Pope Gregory VII granted absolution and removed a ban of excommunication from him. Henry had been at odds with the papacy over ultimate control within the Holy Roman Empire. His penance greatly strengthened his hand against the German princes who threatened him, for they had been allies of the pope and when Henry was absolved the princes withdrew their support for Gregory.