The _specus_ passed upon an arch over the road in the old foss outside the wall into a garden on the opposite side, where it can be seen on the level of the ground; thence it can be traced through that large garden or vineyard as far as the railway, which passes on the outer side of it in a deep cutting. The remains of the brick arcade here form a wall between this garden and another. It is covered with shrubs, and looks like a hedge, from which circumstance it has hitherto escaped observation. The wall is cut through by the railway, but can be traced on the other side of it along the bank of a narrow deep lane, like what we call in England a Devonshire lane. This lane goes parallel to the Via Latina, on the southern side of it, for about a mile; the aqueduct then leaves it, turning short to the left. Near to this angle, at about half-a-mile outside of the Porta Latina, is a large reservoir belonging to this aqueduct. It is built against the western cliff of the valley of the Caffarella, the top of it level with the summit of the cliff, and therefore is not visible from above, as a person standing on the higher ground looks over it. It is also hidden by a clump of trees; but it is very distinctly visible from the valley below, and from some parts of the Via Appia, and is readily seen to be a _castellum aquæ_ by the boldly-projecting buttresses to support the wall with the weight of water behind it. The Aqua Antoniniana ran along the edge of the cliff, and supplied this large reservoir, which is oblong as usual, and divided down the middle by an arcade, similar to the fine one of the Marcian near Tivoli, and many others. This has been plastered over, and made into a cow-house. It is far above the level of the Aqua Aurelia, which runs below along the side of the valley of the Caffarella. The Aqua Antoniniana clearly came from the higher aqueducts in the main line; and, according to the Einsiedlen Itinerary, it was a branch of the Marcian which went to supply the Thermæ of the Antonines called that of Caracalla. Part of the brick arcade, with the _specus_ upon it, is here visible in another garden against a cliff; it then passes underground for a short distance, but soon emerges again, and can be traced against another cliff as far as the Via Latina, which is here upon a bank, or rather on the edge of higher ground, with the remains of a _piscina_ by the side of it. The _specus_ then again passes underground for some distance, and the next point where we have been able to find it is an old stone quarry, the vault of which fell down in 1870, and revealed this _specus_, which was not visible before. This is in the garden behind the Albergo de’ Spiriti, on the Via Appia Nova, about two miles from Rome, and near the point where it crosses the old Via Latina[184].