The intrados of the southern arm, preceding the lunette depicting the martyrdom of Saint Lawrence, is adorned with a double-perspective meander, formed by double-round swastikas and squares outlined by rows of white tesserae. The tiles are brightly coloured and arranged in large fields.
This type of decoration has very ancient roots. It is named after the Meander, an Anatolian river with a winding course, which flowed through Phrygia and into Miletus. It was used in Greek art as a decorative motif to emphasise key points or thresholds, as seen in the Ara Pacis in Rome. In Ravenna, it introduces one of the main figurative mosaics and the swastika is understood to be related to the cult of light, the sun and Christ – Sol Invictus.
In the sacellum of Saint Aquilinus, in Milan, a marble slab features this same motif, deeply carved, and probably filled with coloured glass or glass paste, imitating the jewellery of Oriental origin, with a vibrant mosaic-like effect.