The Mausoleum of Galla Placidia is a Roman building in Ravenna, oiginally the oratory of the Church of the Holy Cross.
See:
- Andre Grabar, L'Âge d'or de Justinien, de la mort de Théodose à l'Islam, Paris 1966
- https://en.wikipedia.org/wiki/Mausoleum_of_Galla_Placidia