The West (Gridiron) Apse at the Mausoleum of Galla Placidia: Detail, saints and doves

The doves approaching the fountain in a footed bowl resemble the more common motif in which a bowl/fountain is approached by peacocks. The motif is a way of expressing both the thirst of the repentant for healing and the promise of immortality. (See my essay on fountains and peacocks.) In the corresponding lunette in the east apse two doves drink from a similar footed bowl.

The two men in togas may be apostles. The corresponding image in the east apse across from this one has Peter and Paul, similarly dressed.

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Photographed at the site by Richard Stracke, shared under Attribution-NonCommercial-ShareAlike license.