In a quiet corner of Rome stands the church of Santa Costanza, which was originally the Mausoleum of Constantia and her sister Helena, daughters of the emperor Constantine the Great (r. 306-337).
The central space is surrounded by an ambulatory, made up of 24 pairs of granite columns. The barrel vaulting of the ambulatory is decorated with a series of remarkable mosaics (4th century).
The mausoleum was transformed into a baptistery before becoming a church in 1254.
Both Constantia and Helena were interred here. Constantia's monumental porphyry sarcophagus is now on display in the Vatican Museums, Helena's has not survived.