From Erika Simon, Die Konstantischen Deckengemälde in Trier

Helena? A diademed woman appears in this fourth-century fresco from the ceiling of Constantine’s palace in Trier, Germany. In one hand, she holds the transparent scarf that covers her hair; in the other, an elaborate silver bowl. The palace fresco clearly portrays a royal woman from Constantine’s court, and thus may well depict Helena, who moved to Trier to be with her son in about 306 C.E. The empress was so popular there that medieval legend identifies Trier as her birthplace (in truth, she was probably born in northwestern Turkey). The fresco (and the palace) was discovered during excavations beneath the cathedral of Trier. Local legend suggests that the devout Helena donated the palace to the bishop of Trier to transform into a cathedral.