Santa Maria Antiqua sits on the foot of the Palatine hill in Rome, a church dedicated in the 6th century and originally integrated into the imperial palace complex from the time of Domitian (81-96 AD). It is one of the first buildings of the Forum Romanum to have been converted into a church. Buried under sediments by an earthquake in 847, the church remained sealed until January 1908 when it was rediscovered and excavated (you can find more details and pictures on this website specially created by the authorities of Rome to preserve archaeological sites of the City).
What makes this church so important are its frescoes, dating between the 6th and the 9th centuries, first because they allow us to trace the evolution of religious art over several centuries, particularly those centuries which saw the Iconoclast crisis in the Byzantine empire and which resulted in the destruction of much art. Most frescoes date to the Byzantine period of Rome, with Eastern (Greek, Sicilian, and Syrian) popes being especially active in promoting art in the Eternal City–an art which necessarily was heavily influenced by Byzantine models. But also, a particular fragment, dated to the early 7th century, casts light on the fate of Hellenism in art in Late Antiquity (see images below).
The palimspest (wall to the right of the apse) preserves no less than seven layers of superimposed frescoes, most of which are today fragmentary, but which allow nonetheless for opening a window on the various styles that have developped over some four centuries, from the 4th century when the building was not yet a church to the eigth century. The fourth layer depicts the Annunciation and is dated to the early seventh century. The face of the angel is clearly visible and has been nicknamed, on account of its fairness, the ‘fair angel,’ or sometims the Pompeian angel, given the similarities with figural representations seen in the buried city. The style of the angel (the calm demeanor, the soft strokes, the shading giving a three-dimensional figure) arches back to Classical Antiquity, and indeed looks to the Renaissance itself. The style is both classical and modern. The Virgin Mary, looking right toward the angel, is painted in the same style and is visible to the left of the angel, above the halo.