The construction of the Anio Vetus, occurring merely forty years after that of the Appia, was an ambitious undertaking. Its course was approximately four times the
length of the Appia and the source was much higher than the Appia. In time it became known as the 'Old Anio'. Funded by the spoils of the Pyrrhic war, it was constructed
between 272 and 269 BC. The source is the river Anio, a tributary of the Tiber, in the upper Anio valley, and was the first of four to take water from that place. Frontinus
states that "the intake of the Old Anio is above Tibur at the twentieth milestone...", which is too low a figure, whereas it is too high a figure if Tivoli is meant. Most
archaeologists believe its source to be between Vicovaro and Mandela, 850 metres upstream of the gorge at S. Cosimato. The intake, off a basin filled by river water,
was 260 metres above sea-level (Aicher, 1995:35). Ashby (1935:57) concludes that Frontinus was mistaken in the length of the Anio Vetus.
Course
Like the Aqua Appia, the Vetus' course was primarily underground. Later, however, as technology advanced, the addition of bridges and substructures shortened its
course to between 64 and 81 kilometres. Frontinus records the lower number, Blackman (1979) states this is too low and gives the higher figure. The Vetus' general
path to Rome became the template for future aqueducts, except for its supplementary channel that took short cuts to avoid the paths along the sides of valleys. From
its source it descended along the river to Tivoli where it left the Anio valley and sloped south towards the Alban Hills to near Gallicano, below Palestrina. From here
turned west again towards Rome. It crossed under the Via Latina near the 7th mile marker, southeast of the city, near the terminal subway station at Anagnina. At the
4th milestone the aqueduct turned northwest to enter Rome.
Distribution
Ponte Taulella
After entering the city underground via the Porta Praenestina it terminated inside the Porta Esquilina. Frontinus states that the aqueduct served the following areas:
the Porta Capena, Isis and Serapis, Templum Pacis, Esquiliae, Alta Semita, Via Lata, Forum Romanum, Circus Flaminius, Piscina Publica, and Transtiber. Both the
Vetus and the Appia served the Forum Romanum and Circus Flaminius, thus alluding to the increased needs of the city's centre, particularly the subura, an area which
could not be supplied by the Appia alone; on account of its low level and terminal position near the Tiber. Frontinus documents that only 5.8% of the Vetus' total
distribution supplied imperial buildings. This illustrates an important difference with the Appia, which gave almost 22% to such buildings. Approximately 44% of the
Vetus' volume was delivered to the privati located on the eastern hills. A remaining 49.8% supplied the usibus publicis. Included in this category are fountains and
industrial and irrigation areas. Water was reserved for the latter two areas so that the Marcia was free to supply public taps and water troughs for animals. It is important
to note that the water, due to its poor quality, was used primarily for public baths, gardens and industry. The water was muddy after storms, and cloudy even in good weather.
Frontinus estimated that the Anio Vetus delivered 180,000 m3 per day (Aicher, 1995 and Frontinus).
Complementary to the Aqua Appia
The Vetus approached the city in the same fashion as the Appia; underground near the Spes Vetus and distributed its water inside a gate of the Servian Wall. The Vetus
and the Appia complement each other in a fashion that suggests the careful planning of the Vetus. The aqueducts serviced two of the same regions due to the increased
demands, however, they also fuel separate areas with regards to the low and high lands of the city. However, the two aqueducts differed considerably in construction.
The Vetus was much more complex in design, for it incorporated a piscina, drew some of its water from the Marcia, and supplied a branch line of its own called the 'specus
Octavianus'. Frontinus indicates that the Vetus had 35 'castella', indicating its widespread distribution. The Vetus, however, probably did not supply the drinking
water to the Roman aristocracy. Confirmation of this hypothesis is found in Frontinus' discussions regarding the quality of the water in the Vetus line. Frontinus indicates
that the Vetus had 'muddy water' and goes on to state that the aqueduct did not pollute the lines of later aqueducts that ran similar courses )1. This alludes to the fact that
the Vetus ran beneath these future lines and thus did not have the ability to service the higher locations within the city (Aicher, 1995 and Frontinus).
Branches
There are two known branches of the Vetus. The branch known as the 'specus Octavianus' diverted from the Vetus less than four km from Rome. Augustus
erected the only 'cippi' recorded for the Anio Vetus, and it was no doubt he that constructed this branch (Ashby, 1935:55). There are now no known remains left of the
'specus Octavianus'. The other branch is only mentioned by Livy once, on the work knows as the Oxyrhynchus Epitome, in book 54.
)1 Perhaps the muddy water was the reason for the 'piscina' less than 8 km from Rome, as mentioned by Frontinus (1.15). It is also probably the 'Castellum
Viae Latinae contra dracones' mentioned in the inscription CIL 6.2345.
