The inspection of these _graffiti_, then, is enough to warn us that we are on the threshold of a very special sanctuary of the ancient Church, and to excite our deepest interest in all that we may find it to contain. But our first impression on entering will probably be one of disappointment. We were led to expect that we were about to visit a Christian burial-place and place of worship of very great antiquity, but the greater part of the masonry we see around us is manifestly of quite recent construction. The truth is, that when this chamber was rediscovered in 1854, it was in a complete state of ruin; access was gained to it only through the _luminare_, which, as usual, had served for many centuries as a channel for pouring into it all the adjacent soil, fragments of grave-stones from the cemetery above-ground, decaying brickwork, and every kind of rubbish. When this was removed, the vault of the chamber, deprived of its usual support, soon gave way; so that, if any portion of it was to be preserved and put in a condition to be visited with safety, it was absolutely necessary to build fresh walls, and otherwise strengthen it. This has been done with the utmost care, and so as still to preserve, wherever it was possible, remains of the more ancient condition of the chapel and of its decoration in succeeding ages. Thus we are able to trace very clearly in the arch of the doorway three stages or conditions of ornamentation by means of three different coatings of plaster, each retaining some remnant of its original painting. We can trace also the remains of the marble slabs with which, at a later period, the whole chapel was faced; and even this _later_ period takes us back to the earlier half of the fifth century, when, as the _Liber Pontificalis_ tells us, St. Sixtus III. _platoniam fecit in Cœmeterio Callixti_. The fragments of marble columns and other ornamental work, which lie scattered about on the pavement, belong probably to the same period, or they may have been the work of St. Leo III., the last pontiff of whom we read that he made restorations here before the translation of the relics by Pope Paschal I. Again, the raised step or dais of marble, which we see directly opposite to us at the further end of the chapel, having four holes or sockets in it, was of course found here as it now is, and it shows plainly where the altar once stood, supported on four pillars; but in the wall behind this platform we seem to detect traces of a yet older and more simple kind of altar—a sepulchre hewn out of the rock, the flat covering of which was probably the original _mensa_ whereon the holy mysteries were celebrated in this place.