What church plan was used as the model for the palace chapel at Aachen?

The palace chapel at Aachen, built by Charlemagne, was modeled after the Church of San Vitale in Ravenna, Italy. This design features an octagonal shape, a central dome, and intricate mosaics, reflecting Byzantine architectural influences. The chapel served as a symbol of Charlemagne's power and his desire to establish a Christian empire in the West. Its innovative design also influenced subsequent Carolingian and Romanesque architecture.