The Church of _SS. Cosmo and Damiano_ was founded within the ancient temple by Pope Felix IV. in 527, and restored by Adrian I. in 780. In 1633 the whole building was modernized by Urban VIII., who, in order to raise it to the present level of the soil, cut the ancient church in half by the vaulting which now divides the upper and lower churches. To visit the lower church a monk must be summoned, who will bring a torch. This is well worth while. It is of great size, and contains a curious well into which Christian martyrs in the time of Nero are said to have been precipitated. The tomb of the martyrs Cosmo and Damian is beneath the altar, which is formed of beautiful transparent marble. Under a side altar is the grave of Felix IV. The third and lowest church (the _original_ crypt) which is very small, is said to have been a place of refuge during the early Christian persecutions. Here is shown the altar at which Felix IV. celebrated mass while his converts were hiding here--the grave in which the body of the pope was afterwards discovered--and a miraculous spring, still flowing, which is said to have burst forth in answer to his prayers that he might have wherewithal to baptize his disciples. A passage which formerly led from hence to the Catacombs of St. Sebastian, was walled up, twenty years ago, by the paternal government, because twenty persons were lost in it. In this crypt were found the famous "Pianta Capitolina," now preserved in the Capitol. In the upper church, on the right of the entrance from the circular vestibule into the body of the building is this inscription-- "L'imagine di Madonna Santissima che esiste all'altar magg. parlò a S. Gregorio Papa dicendogli, 'Perchè piu non mi saluti mentre passando eri solito salutarmi?' Il santo domandò perdona e concesse a quelli che celebrano in quell'altare la liberazione dell'anima dal purgatorio, cioé per quell'anima per la quale si celebra la messa."[63] Another inscription narrates-- "Gregorius primus concessit omnibus et singulis visitantibus ecclesiam istam sanctorum Cosmæ et Damiani mille annos de indulgentia, et in die stationis ejusdem ecclesiæ idem Gregorius concessit decem millia annorum de indulgentia." Among the many relics preserved in this church are, "Una ampulla lactis Beatæ Mariæ Virginis"; "De Domo Sanctæ Mariæ Magdalenæ"; "De Domo Sancti Zachariæ profeta!" Deserving of the most minute attention is the grand mosaic of Christ--coming on the clouds of sunset.