The Mausoleum of Galla Placidia in Ravenna, built around 425-450 CE and named for the Western Roman empress who was likely its patron, houses the oldest surviving intact mosaic program in the Western world. The building is a small cross-shaped brick structure, unimpressive from the outside, but the interior is among the most beautiful spaces produced by the late antique Christian world. Every surface is covered with mosaic: the walls in blue-gold arabesques and figural panels, the vault lunettes in intense narrative and symbolic scenes, the ceiling vault in a deep lapis lazuli blue scattered with gold stars around a golden cross at the center.
The programmatic heart of the mosaics is the Good Shepherd lunette above the entrance, directly visible to those entering: Christ as a young beardless shepherd sits among his flock, robed in gold and purple rather than the simple shepherd's garment of earlier Christian art, holding a long golden cross-staff rather than a crook. The six sheep arranged around him are attended to individually - Christ reaches out to touch the nearest one. The image draws on John 10:11-16, where Christ says 'I am the good shepherd. The good shepherd lays down his life for the sheep... I know my sheep and my sheep know me.' The golden garments transform the humble pastoral image into an image of royal divine sovereignty: the shepherd of John 10 is also the King of Revelation.
The connection to Revelation 21-22 is explicit throughout the mosaics. The deep blue of the vault - a blue achieved with genuine lapis lazuli, one of the most expensive pigments available - represents the heaven of God's dwelling. The gold stars scattered across it render Psalm 19:1 ('The heavens declare the glory of God') as direct visual statement. Revelation 21:23 describes the New Jerusalem as a city that 'does not need the sun or the moon to shine on it, for the glory of God gives it light, and the Lamb is its lamp' - and the Galla Placidia mosaics create an interior in which that divine self-luminosity is made experientially real. When the natural light through the thin alabaster windows combines with the reflective gold tesserae, the interior appears to generate its own light.
The technical achievement of the mosaics is inseparable from their theological effect. The tesserae - small cubes of colored glass and stone set at slightly varying angles to each other - catch and redirect light differently depending on the viewer's position and the direction of the light source. This means the mosaics are never the same twice: they shimmer and shift as the viewer moves or as the sun moves. The effect is precisely what late antique aesthetic theory, informed by Neoplatonist philosophy, associated with the divine: a beauty that cannot be fixed or possessed, that exceeds any particular visual moment.
Galla Placidia (388-450 CE) was one of the most powerful women of the late Roman world - daughter of Theodosius I, sister of two emperors, mother of Valentinian III, regent for her son during his minority, and a major force in the politics of both the Eastern and Western empires. Whether she was actually buried in the mausoleum named for her is uncertain: she died in Rome and was probably buried there. The three sarcophagi preserved in the building are more likely those of other members of the imperial family. But her patronage of the building - and of the broader program of sacred architecture and mosaic art in Ravenna - is well-documented.
The mausoleum's mosaic program is organized around four lunettes and the central vault. The lunette opposite the Good Shepherd shows St. Lawrence approaching a gridiron (the instrument of his martyrdom) with a large golden cross and open gospel books - a martyrdom image that connects the sacrificial death of the saint to the death of Christ. The two lateral lunettes show deer drinking from a pool (Psalm 42:1: 'As the deer pants for streams of water, so my soul pants for you, my God') - an ancient baptismal image connecting the thirst for God to the waters of baptism. The central vault's blue and gold achieve the experience of the heavenly court of Revelation 4.
The building is now a UNESCO World Heritage Site and among the most visited monuments in Ravenna. It stands adjacent to the Basilica di San Vitale, and the two buildings together offer a concentrated experience of the finest early Byzantine art in the Western world. The mausoleum is small - only a few visitors can be inside at once - which intensifies the enveloping quality of the mosaics.
For further reading: Deborah Mauskopf Deliyannis, Ravenna in Late Antiquity (2010); Jaś Elsner, Imperial Rome and Christian Triumph (1998); Ernst Kitzinger, Byzantine Art in the Making (1977); Gillian Mackie, Early Christian Chapels in the West: Decoration, Function and Patronage (2003); Richard Krautheimer, Early Christian and Byzantine Architecture (1986).