Stational liturgy and local history : Leo III's Apse mosaic at Santa Susanna

A now-lost apse mosaic commissioned around 800 by Pope Leo III (r. 795–816) for the church of Santa Susanna depicted John the Baptist and John the Evangelist on the arch, and nine figures in the vault, including the Virgin Mary and Charlemagne. The lost decoration is thus an updated version of the traditional Roman seven-figure apse-mosaic configuration. In an attempt to reconstruct the missing mosaic, this study relies on late-sixteenth- and seventeenth-century descriptions that shed light on the relationship between the mosaics and Pope Hadrian I's (r. 772–795) murals discovered in 1991 under Santa Susanna's current sacristy. The study aims to clarify the iconographical choices that Leo iii opted for. This is accomplished, on the one hand, by focusing on early-medieval Roman stational liturgy, repeated at Santa Susanna on the third Saturday of Lent from the late-fifth century on. On the other hand, the apse mosaic is explained in light of the church's local history, which was well known to Leo III.