A very remarkable feature in the Catacomb of S. Priscilla are the reservoirs of water, which evidently served in very early days as baptisteries. The most considerable of these reservoirs or tanks is on the upper story of the cemetery, and is communicated with by a broad staircase of over twenty-five steps, which come out behind what was once the apsidal end of the Basilica of S. Sylvester. Marucchi describes it as “une vaste piscine encore pleine d’eau, desservie par un petit canal.” This great baptistery became, from the fourth century onward, a spot of intense interest to the many pilgrims who visited the catacomb sanctuaries. Another large reservoir of water has been found on the second story of this vast catacomb; other and smaller tanks have also been found. Marucchi believes that this cemetery is the one alluded to in the many traditions, including the notices in the Pilgrim Itineraries, as the special scene of S. Peter’s labours and preaching, teaching and baptizing, as the “cœmeterium beati Petri ubi baptizaverat,” as the “sedes ubi prius sedit sanctus Petrus.” The investigation which has led to recent discoveries in this cemetery had not been completed when De Rossi identified the Cœmeterium Ostrianum (of which we spoke above) as the scene of S. Peter’s work. It is these latest “finds” that have induced Marucchi to fix the Priscilla Cemetery as the place where the great apostle laboured in those early years of the history of Roman Christianity. Beneath the first vast gallery of this catacomb with its many memories of saints and martyrs, including the famous crypt of the “Acilii Glabriones” house, lies another and very ancient area of sepulchral galleries. This area was communicated with by several staircases, some of which are now completely closed. This vast sepulchral area has been as yet only partially explored. It is described roughly as consisting of a long gallery, out of which lead more than twenty other galleries, many of which as yet are only imperfectly investigated. Marucchi, who has devoted a long and important section of his great work to the Priscilla Catacomb, writes of this second story of the cemetery as the most extensive and carefully planned of all the cemeteries of subterranean Rome that have been yet examined. His words here are remarkable, and must be quoted: “On peut dire sans exaggeration, que c’est la région cemétériale la plus vaste et la plus régulière de toute la Rome souterraine.” The masonry used in its construction; its many inscriptions on the loculi, carved in marble, or painted in red on tiles,--all bear witness of its hoar antiquity; much of it dates certainly from the second century. It contains, as we have remarked already, a reservoir or tank of water--of course a baptistery--deep and of considerable size.