Before leaving this division of our subject we will take a rapid survey of the more remarkable of that vast system of Christian cemeteries that engirdles the city of Rome. It will be more convenient to notice them in topographical order, beginning with those on the Appian Way, and sweeping around the city to the north-west, over the great roads on the borders of which the Catacombs are chiefly situated. The ground near these roads is honeycombed with sepulchral excavations, to which there are said to be six hundred entrances scattered over the Campagna. Bosio found them in almost every vineyard near the Salarian Way. In some of these the peasants keep their wine, although their fears prevent them from venturing far from the mouth; and sometimes villas fall in through the subsidence of the soil. The various groups of crypts have been known by different names at different periods, or even at the same period; and it is sometimes difficult or impossible to disentangle the conflicting accounts, and to identify the cemeteries to which the ancient names were applied. The original records--the martyrologies and the _Liber Pontificalis_[291]--are sometimes utterly unreliable, and the very existence of the saints and martyrs whose lives are recorded is 165 often exceedingly apocryphal; and even if their traditions are in the main correct, it is in many cases doubtful if they are buried in the Catacombs which bear their names. Frequently, however, these traditions are confirmed by inscriptions and other monumental evidence, which establish beyond doubt the identity of the Catacomb, as in the case of that of Callixtus and others which we shall notice. [Illustration: Fig. 25.--Tombs on Appian Way.]