The word _rediculo_ is supposed by some to come from _redeo_, I return, as applied to the spot where Hannibal turned back from Rome; but from Pliny we know there was a place called Campus Rediculi, and that it was to the right of the Via Appia in coming out of the city, so it could have nothing to do with this field. Pompeius Festus, a Latin critic of the fourth century, ascribes it to the above meaning, but he would be no authority. Hannibal's camp was on the road to Tivoli, and from there he returned. "Hannibal moved his camp forward to the river Anio, three miles from the city. Posting there his troops, he himself, with two thousand horsemen, proceeded from the Colline Gate as far as the Temple of Hercules, riding about, and taking as near a view as possible of the situation and fortifications of the city" (Livy, xxvi. 10). "Discouraged by all circumstances, he moved his camp to the river Tutia, six miles from the city" (_Ibid._, xi.). The tomb is built of yellow bricks, with red brick basement, pilasters, and ornaments: on one side is the pediment of the portico, which was formed with peperino columns. Over the square doorway is a decorated niche for the statue. The tomb contained originally two chambers, but the flooring of the upper one has been destroyed--thus making one--the vault of which was decorated with stucco ornaments. In construction it is like the painted tombs on the Via Latina, the bricks being carefully baked and laid with very little mortar between them, not unlike the entrance to some of the warehouses at Ostia, and of the same date--time of Hadrian; for being a tomb, and not cased with marble, it shows more careful construction than the ordinary brickwork of the time of that emperor. Proceeding on our ramble along the Via Appia, _upon the left_ is an unknown tomb; _on the right_, beyond, another. This is exactly at the second mile from the Porta Capena. Here was the Campus Rediculi. Was this the raven's tomb? (See page 18.) The vineyard on the left contained the Columbaria of Livia, now destroyed. _Beyond_, entrance to the Catacomb of Prætextatus. _Upon the right_, TOMB OF THE CÆCILII, a shapeless mass of rubble. Several epitaphs to this family have been found here. _Just beyond is the entrance to the_ CATACOMBS OF S. CALIXTUS. _Fee, one lira each, which includes guides and lights._ Catacomb is a medieval word, and is said by some authorities to be derived from the Greek words κατὰ, under, and κύμβος, a hollow. The Romans called these burial-places cemeteries. They generally consist of three strata of tufa: _litoide_, of a red conglomeration, hard, used for building; _pozzolana pura_, a friable sand, for mortar; and _granolare_, harder, but easily cut, of which the catacombs were almost exclusively made.