This fourth milestone was clearly on the Via Latina, as Frontinus in the previous paragraph had referred to some _piscinæ_ at the seventh milestone on the same road; and it appears, although the sentence is exceedingly corrupt, that the course of the Aqueduct left the Via Latina at this point, and crossed towards the Via Labicana “amongst the arches[37]” at the fourth milestone. The _specus_ is here visible, and appears to be perfect; it is very near to the Torre Fiscale[38], between that and the Osteria, called the Tavolato (which itself appears to be made out of another, but a later, reservoir belonging to the aqueducts, as many of the houses in the Campagna have been). The vault of the old _castellum aquæ_ or _piscina_ is now covered with turf, but the side of it forms a sort of cliff like the edge of a quarry. This place, where the Anio Vetus leaves the Via Latina, is near the great junction and crossing of the aqueducts, over which the tall medieval tower called the Torre Fiscale has been built. Here six aqueducts meet and cross each other. The Marcian arcade, with three of these, makes one of its many angles, and the lofty Claudian arcade, with two more, is carried over it. The expression that it passed amongst the arches is a very natural one, to any person who knows the locality, as there are many arches at this point. It then goes on to another angle and crossing of the great aqueducts, where there is a gate called Porta Furba, about two miles and a-half from the Porta Maggiore. There is a _castellum aquæ_ of the time of Nero, with an ancient _piscina_ under it, and a fountain of Sixtus V. by the side of it. At the second milestone it parted with some of its water into the _specus_ called the _Octavian_, which enters Rome at the Asinian gardens, following the direction of the new road. By referring to the maps it will be seen that the original line of the Via Latina united with the Via Appia within the outer wall and before reaching the old southern entrance of the city (the Porta Capena); but, in joining this latter road (the most convenient course to pursue in the then state of the fortifications), the Via Latina swerved rapidly to the south-west. Had it been continued in a direct line, it would have reached the Cœlian Hill, near the Porta Asinaria, as the Via Appia Nova still does, following the line of the old Via Asinaria.