The soft light from the windows in the clerestory give a wonderfully peaceful aura to this austere little church of the fifth century. A swingeing restoration in 1925 did away with centuries of decoration and restored its original Romanesque simplicity. The 16 columns, pilfered from the Palatine and the Aventine hills, are all different. Pieces of an eighth- or ninth-century choir, including two slender columns, are incorporated into the walls. In the apse is a much-restored fresco by the school of Pietro Cavallini showing St George with a white horse and the Virgin on one side of the central Christ figure, and St Peter and St Sebastian opposite.
The 12th-century altar is a rare example of the Byzantine-inspired 'caged and architraved' ciborium, a canopy on columns. A church was first built here by Greeks and was dedicated to St Sebastian, who was believed to have been martyred in the swampy area hereabouts. It was later rededicated to St George of Capadoccia (of dragon-slaying fame); a piece of the skull of the valorous third-century saint is kept under the altar. The portico and bell tower are 12th-century additions. Outside, to the left, is the arco degli Argentari, built in AD 204; it was a gate on the road between the main Forum and the forum boarium (cattle market), along which moneychangers (argenteri) plied their trade. The church and other monuments were damaged by a Mafia bomb in 1993 but have since been repaired.