Complex sentence: His complex at Germigny-des-Prés was in a general sense modelled on Charlemagne's palace complex at Aachen; all except the oratory was destroyed by the Normans (then just emerging from the Vikings) within a century of construction.
Split into simpler sentences: His complex at Germigny-des-Prés was in a general sense modelled on Charlemagne's Palace of Aachen. All except the oratory was destroyed by the Normans (then just emerging from the Vikings) within a century of construction.