At the left side of the chapel between the columns is the reliquary altar of Santa Galla. The original, from the Flavian period, probably comes from the temple of Apollo Sosiano or Medicus and is now kept in the church of Santa Galla on Via Ostiense. It was reused in medieval times as a high altar of the ancient church of Santa Maria in Portico. The inscription of the altar contains a long list of relics: the fragments of the cross of Christ and the sponge, of the cross of St. Andrew and parts of his bones, and the relics of 21 other martyrs including 6 women.