Exterior view

The mausoleum is a small cruciform structure with a high centre bay surmounted by a pendentive dome and giving access to four low barrel-vaulted arms all sheathed in figural mosaics. It was erected as an ante-chapel of the church of Santa Croce (destroyed) and dedicated to St Lawrence. Its plain exterior of blind arcades and pilasters contrasts with the predominant blue, green, and gold interior, which contains one of the best-preserved Early Christian mural mosaics.

The building was almost certainly not used as the tomb of Galla Placidia. Galla Placidia (388-450) was the daughter of the Roman emperor Theodosius I, was regent to Valentinian III from 423 until his majority in 437, and a major force in Roman politics for most of her life. She was queen consort to Ataulf, king of the Visigoths from 414 until his death in 415, and briefly empress consort to Constantius III in 421.

View the isometric representation of the building connected to the destroyed church of Santa Croce.