Aqua Traiana
The Aqua Traiana (later rebuilt and named the Acqua Paola) was a 1st century Roman acqueduct built by Emperor Trajan and inaugurated on 24th June 109 AD. It channelled water from sources around Lake Bracciano, 40 kilometers (25 mi) north-west of Rome, to Rome in ancient Roman times but had fallen into disuse by the 17th Century. It fed water mills arranged in a parallel sequence at the Janiculum, under the present American Academy in Rome. The milling complex had a long history, and were famously put out of action by the Ostrogoths when they cut the aqueduct in 537 during the first siege of Rome. Belisarius restored the supply of grain by using mills floating in the Tiber. The complex of mills bear parallels with a similar complex at Barbegal in southern Gaul.

Original Sources of the Aqueduct
Both the ancient Aqua Traiana, and the modern Acqua Paola were fed by a collection of aquifer sources in the hills around the volcanic basin of Lake Bracciano. The original primary source of the Aqua Traiana is located by Carlo Fea (1832) as close to a stream in the modern district of Manziana. Fea makes reference to a document written by the architect Luigi Bernini on 25th February 1667 to Pope Alexander VII Chigi. The Manziana source has never formed part of the modern Aqua Paola, but in 1667, Alexander VII wanted to add additional water to the Acqua Paola to power his new fountain in St. Peter's Square. Bernini measured the water at this source as supplying 340 "oncie" of water of perfect goodness and lightness. This water was sufficiently copious, according to his calculation, to double the yield of the Acqua Paola. It supplied as much water as all the rest of the sources put together. However the Manziana water had, since the 1570s been diverted to supply the mills and industry of the rogue duke Paolo Giordano Orsini in the nearby dukedom of Bracciano, so neither Pope Paul V in the early 1600s, nor Pope Alexander VII three quarters of a century later were able to purchase this particular source, and it remains to this day independent from the modern aqueduct. In the same year that Luigi Bernini wrote his report, the Pope died, and the project was shelved, so the modern aqueduct was eventually supplemented with lake water. The addition of the Lake Water makes Acqua Paola water unhealthy to drink, and gives it a bad taste, which has caused the roman saying that something of bad quality is "as good as the Acqua Paola". The Manziana source was re-identified in early 2009 by two British film-makers and it's identity was confirmed on 24th June 2009, on the exact anniversary of 1900 years after the aqueduct's inauguration by archaeologist Lorenzo Quilici of University of Bologna.

Revival as Aqua Paola
Camillo Borghese, on his accession in 1605 as Pope Paul V, initiated work on rebuilding the Aqua Traiana, supervised from 1609 by Giovanni Fontana. At that time, the Roman suburbs west of the Tiber River, including the Vatican, were suffering from chronic water shortage. The new pope persuaded the Municipality of Rome to pay for the development of an acqueduct to provide a better water supply to that part of the city. In 1612, the acqueduct was completed. It was initially called the Acqua Sabbatina or Acqua Bracciano, but was renamed Acqua Paola in honour of Paul V. The fountain at the end of the acqueduct was referred to as "Il Fontanone" - the Big Fountain - because of its size. It was a the form of a free-standing triumphal arch constructed in white marble with granite columns on high socles. Most of the material was pillaged from the Forum of Nerva. Originally, it consisted of three large central arches, separated by columns, and a smaller one on each side. Water gushed into five basins at the base of each arch. The designer was Paul V's usual architect, Flaminio Ponzio. Among the team of sculptors involved was Ippolito Buzzi, who was responsible for the Borghese coat-of-arms, flanked by the Borghese eagle and dragon and held aloft by putti, doubtless to Ponzio's design. Then, in 1690, Pope Alexander VIII commissioned Carlo Fontana, Giovanni's nephew, to enlarge the fountain. Carlo replaced the five small basins with an enormous single one which remains to this day. In more recent times a small garden has been arranged, hidden behind the structure.