The excavation of an ancient cave sanctuary beneath the theatre castle has led to the discovery of human terra cotta limbs and mythological marble sculptures. The marbles were deposited in late antiquity, and the circumstances illuminate the process of Christianisation. Dozens of fingers and other life-size limbs of burned clay may be identified as votive offerings for the cure of the respective limbs. They indicate that the cave was a healing shrine. It is centred on a karst spring that will have played a key part in the cure, but was filled in and blocked in the 4th/5th century AD. This probably happened after emperor Theodosius I had banned the ancient cults. The spring was filled in with half a dozen mythological marble sculptures that were deposited together with oil lamps and covered with roof tiles. The sculptures are missing noses and ears that had already been chopped off, probably by Christians, before the marbles were buried. Their deposition in the cave will have served to protect them from further damage. This seems to be confirmed by the oil lamps that were deposited together with the sculptures and suggest a proper burial ceremony. It may have been the last ritual act that sealed the healing spring and protected it, too, from profanation. Originally, the marbles will not have been displayed in the grotto. They differ in material, size, and stile, but all have fixtures that suggest an architectural context such as, for example, the stage building of the theatre.