Among the wonders of the Metropolis of the World, the catacombs or subterranean vaults and passages are certainly not the least. The first Christians, persecuted with atrocious cruelty by the pagan imperial government of Rome, sought refuge for safety occasionally in the catacombs; and sometimes, also, that they might assemble without incurring suspicion, in larger numbers, to instruct themselves in the doctrines of their new religion. These subterranean passages were also undoubtedly the resort of fugitive slaves and other miserable beings, who sought refuge from the tyrannical government of imperial Rome, over which have presided some of the direst monsters that ever existed--Heliogabalus, Nero, Caligula, and other despots in purple. Among these subterranean passages there are, it appears, different kinds. Some were constructed for the purpose of receiving the dead, others were used as water conduits, and supplied the city with rivers of fresh water for a population of two millions. The cloaca maxima, which led from Rome to the sea, is very famous, as well as many smaller hidden roads, constructed by wealthy private individuals, at an enormous expense, in which they could secrete themselves from the depredations of those greatest of all robbers the emperors, and in later times from the persecution and massacre of the barbarians. The soil on which Rome is built, as well as that in its immediate neighborhood, offers great facilities to the excavator, being composed of volcanic clay, easy to pierce, yet sufficiently solid and impenetrable to damp to form a secure habitation. In fact, to this day many shepherds, with their flocks, lodge in these artificial caverns. Before the exploration of the subterranean passages of the castle, it was thought desirable to send the severely wounded to Rome, attended by those who were only slightly injured, and conducted by some shepherds. Among the Liberals very few were wounded, and none severely so. Many of the Papilini, moreover, requested permission to remain and follow the fortunes of the proscribed, for there are not many Italian soldiers, however debased, who willingly serve the priesthood; and there is no doubt that when the hour for liberating Italy and Rome from their pollution arrives, not a soldier, with the exception of the foreign mercenaries, will remain to protect them. After dispatching the wounded, Orazio and his men removed to the subterranean passages all that the castle contained which was valuable and useful, with provisions of all kinds to last for some time, and then awaited calmly the coming of the enemy. They did not fail to take all military precautions, and that in spite of the notices from Rome of every movement of the enemy, Orazio also sent scouts and placed sentinels in all directions, that he might be apprised at the earliest moment of their approach.