Southeastward from the ancient Porta Capena of the city of Rome stretches the celebrated Appian Way, the most remarkable of those vast arteries of commerce along which flowed to the most distant provinces the vital currents from the great heart of the empire. This “Queen of Roads,”[292] as it was proudly called, was lined on either side by the stately tombs in which reposed the ashes of the mighty dead.[293] “The 166 history of Christian Rome,” says Padre Marchi,[294] “gives to this same road titles of glory incomparably more solid, just, and indisputable. We are forced to acknowledge it as the queen of Christian roads by reason of the greater number and extent of its cemeteries, and still more by the greater number and celebrity of its martyrs.” Under the present pontiff this historic highway has been excavated and opened for travel as far as Albano; and one may now traverse that avenue of tombs on the very causeway on which Horace and Virgil, Augustus and Mæcenas, Cicero and Seneca, must often have entered Rome. But it is invested with a profounder interest as the way by which the great Apostle of the Gentiles approached the city, “an ambassador in bonds,” to preach the gospel in Rome also, and to finish his testimony by a glorious martyrdom. By this very road also, according to an ancient tradition, his body was stealthily conveyed by night and deposited in an adjacent Catacomb; and here wended many a mourning procession bearing to those lowly crypts the remains of Rome’s 167 early bishops, martyrs, and confessors. The ancient Porta Capena, with the dripping aqueduct above it,[295] have disappeared, and the fountain of Egeria, trampled by cattle, is no longer the haunt of nymph or naiad. Passing through the modern Sebastian gate and crossing the classic Almo, the traveller reaches at a short distance the little church of _Domine quo vadis_, with which is connected one of the most beautiful legends of the martyrology.[296] About a mile and three quarters from the city he comes to Vigna Animendola, on the doorway leading to which is a marble tablet with the words COEMETERIVM S. CALLIXTI. Beneath this vineyard lies the celebrated Catacomb of Callixtus, of which we propose to enter into a somewhat detailed description, as it will give greater definiteness 168 to the general conceptions already received, and will serve as typical example of the origin and history of the Catacombs in general.