 The church is also architecturally quite distinct from the Palatine chapel in Aachen, and from S. Vitale in Ravenna – two buildings upon which it is often claimed that SS.Geneviève & Germain is modelled – in that it is square rather than round, has exterior apses and is constructed differently.This is rather a rare survival of a very early form of Western European church, pre-dating and perhaps contributing to the development of the Romanesque which forms the majority of ancient churches in France and, indeed, in Western Europe.The great treasure of the church is the mosaic of the Ark of the Covenant, on the ceiling of the apse.