Charlemagne's Palatine Chapel, from the pictures you have posted, looks stunning and its architectural style depicts Charlemagne's stress on the detail and beautification of this building.  I think it is important to note that despite its outward religious construction, "innovation in arts and literature flourished".  I think  this is essential for future generations to understand where and when such innovations took place in history.  I think it is fascinating that the dome of the chapel depicted the "heavens", similar to that of other religious buildings.  I have recently learned that religious structures like Hagia Sophia and St. Peter's Basilica hold their domes with four tiers.  Do you think the three tiers that hold the dome in Charlemagne's Palatine Chapel are symbolic for the Holy Trinity, or symbolic at all?