Above the entrance, there is a large round-headed window into the chapel. On the cornice in front of this is an ancient vase. This is thought to be the original funerary urn that may have contained her bones, although restored in the 18th century.

The aperture inserts into a large mosaic dominated by blue and gold. Around the aperture are eleven tondi in a golden horseshoe. At the top is the Blessed Virgin Mary holding the Christ Child in front of her, and ten saints of uncertain identity (the top two may be Zeno and Valentine). The blue arch surrounding this has thirteen tondi showing Christ and the apostles, and the last two tondi in the upper corners are thought to be Moses and Elijah. The rectangular panels at the bottom corners are Popes Paschal and his successor Eugene II; these are from the 19th century.