The ancient church of Sant' Agnese fuori le Mura (St Agnes Outside the Walls), which is built over the catacombs where St Agnes is buried, was founded by Pope Honorius I (r. 625-38).
At the back of the church is a narthex for catechumens. The nave is separated from the aisles by 14 ancient columns. There is a matroneum above the aisles and the narthex, the earliest such feature to survive in a Roman basilica. The richly carved wooden ceiling was added by Pope Paul V (r. 1605-21) and restored in the middle of the 19th century. In the centre is St Agnes; the other two saints are St Cecilia and St Constantia.
The glorious mosaics in the apse date back to the reign of Pope Honorius I, while the baldacchino above the high altar was created during the reign of Pope Paul V. The statue of St Agnes is by French sculptor Nicolas Cordier (1567-1612), who used an ancient alabaster torso, to which he added the legs, arms and head in gilded bronze. St Agnes holds a lamb (her attribute) and a palm frond (a symbol of martyrdom).
Beneath the high altar lie the relics of St Agnes and her 'milk-sister' St Emerentiana, who was stoned to death for praying by St Agnes’s burial place.