1. The earliest aqueduct, the APPIA[239] (B.C. 312), being entirely underground at a considerable depth, is marked by a dotted line. It comes from old stone quarries on the bank of the river Anio, just beyond the Caves of Cervaro, about eight miles from Rome, near the ancient Via Collatina, called by Frontinus Prænestina, because in his time the road to Præneste went through Collatia. 2. ANIO VETUS[240] (B.C. 272), comes also from the bank of the river Anio, but at a much higher level than the Appia, between Tivoli and Subiaco, near the village of Agosta, twenty miles from Rome, but the winding course makes the whole length of the aqueduct 42 miles, 779 paces underground, and 221 paces (about 350 yards) above ground on a substructure. It is brought at a considerably higher level than the Appia, but still underground for the most part, though near the surface, and sometimes only half underground. It was not legal to build over an aqueduct anything but another aqueduct, consequently the later aqueducts are all brought on the same line, each on a higher level, so that the line of the Anio Novus, carried on the arches of Nero, shews at the same time the line of the Anio Vetus nearly under it. 3. MARCIA[241] (B.C. 145). This stream also comes from near Subiaco, 39 miles from Rome, 36 on the Via Valeria, and 3 off it on a cross-road, near the village of Arsoli. There is a small lake 38 miles from Rome on the same road (which is another source of this aqueduct), into which the water gushes out from under the limestone rock; it is intensely cold in all weathers, and the water is of a light green colour in the lake. “The length of the course is 61 miles 710 paces, of which 54 miles 247 paces are underground, 7 miles 463 paces above ground, on an arcade for 6 miles 472 paces, on a substructure for 528 paces,” and in several places on bridges across the gorges in the hills. This water was brought into Rome again in 1860-70 by a new line, and was then called Aqua Marcia Pia, from Pius IX.; the name of Pia has since been dropped. 4. VIRGO[242] (B.C. 21), made by Agrippa for his Thermæ, restored to use by the popes in the eighth century, and frequently repaired; now called the Aqua di Trevi, from the fountain so named. The source is on the Via Collatina, 8 miles from Rome and 1 mile beyond the source of the Appia. There are several springs, each with a separate small reservoir, collected in one large reservoir, now under the road. “The length of the course is 14 miles 105 paces.” 5. TEPULA[243] (B.C. 126). The sources of this are 12 miles from Rome, near Grotta Ferrata and Marino, 2 miles from the old Via Latina.