On June 24, 109 AD, Emperor Trajan inaugurated the Roman aqueduct Aqua Traiana. The aqueduct channeled water from sources around Lake Bracciano, 25 miles north-west of Rome, to the city where it fed water mills arranged in a parallel sequence at the Janiculum, under the present American Academy in Rome.
The milling complex was famously put out of action by the Ostrogoths when, in 537, they cut the aqueduct during the first siege of Rome. Belisarius, a Byzantine Empire general, restored the supply of grain by using mills floating in the Tiber River.
The ancient Aqua Traiana was later rebuilt as the modern Acqua Paola. Both were fed by a collection of aquifer sources in the hills around the volcanic basin of Lake Bracciano. In 1832 Carlo Fea located the original primary source of the Aqua Traiana as a stream in the modern district of Manziana.
Camillo Borghese, on his accession in 1605 as Pope Paul V, initiated work on rebuilding the Aqua Traiana. At that time, the Roman suburbs west of the Tiber River, including the Vatican, suffered from chronic water shortage. The new pope persuaded the Municipality of Rome to pay for the development of the aqueduct to provide a better water supply to that part of the city.
In 1612, they completed the aqueduct and called it the Acqua Sabbatina before renaming it in honor of Pope Paul V.
The modern aqueduct was supplemented with lake water making the Acqua Paola water unhealthy to drink, and giving it a bad taste. It gave birth to the Roman saying "as good as the Acqua Paola" when referring to something of bad quality.
To learn about other historic civil engineering projects, visit the People and Projects section of the ASCE website.
• Wikipedia, Aqua Traiana