The conch of the apse is dominated by a bust of Christ emerging from red and blue cloud, flanked by angels. Below hims is the Blessed Virgin standing in prayer, with hands outstretched. She is flanked by (left to right) St Venantius (holding a model of the chapel), St John the Evangelist, St Paul, St John the Baptist, St Domnius and Pope Theodore I in whose reign the mosaic was finished. You need to peer behind the aedicule to see these figures. At the bottom of the conch is an original dedicatory epigraph of Pope John.