What am I looking at?
The Trevi Fountain (Italian: Fontana di Trevi) is an 18th-century fountain in the Trevi district in Rome, Italy, designed by Italian architect Nicola Salvi and completed by Giuseppe Pannini in 1762.
The quick answer
The Trevi Fountain (Italian: Fontana di Trevi) is an 18th-century fountain in the Trevi district in Rome, Italy, designed by Italian architect Nicola Salvi and completed by Giuseppe Pannini in 1762. Standing 26.3 metres (86 ft) high and 49.15 metres (161.3 ft) wide, it is the largest Baroque fountain in the world and one of the most famous fountains in the world.
How it came to be
The fountain, at the junction of three roads (tre vie), marks the terminal point of the "modern" Acqua Vergine—the revived Aqua Virgo, one of the aqueducts that supplied water to ancient Rome. In 19 BC, supposedly with the help of a virgin, Roman technicians located a source of pure water some 13 km (8.1 mi) from the city. (This scene is presented on the present fountain's façade.) However, the eventual indirect route of the aqueduct made its length some 22 km (14 mi). This Aqua Virgo led the water into the Baths of Agrippa. It served Rome for more than 400 years.
The detail most people miss
During the 6th century AD, the aqueducts were not well maintained and the 14 functioning ones were damaged during the invasion of the Ostrogoths. Although compromised and greatly reduced in scope after the damage caused by the siege of the Goths of Vitiges in 537, the Acqua Vergine remained in use throughout the Middle Ages, with restorations attested as early as the 8th century, then again by the Municipality in the 12th century, on the occasion of which the conduit was also connected to other sources closer to the city, located in a place then called "Trebium".
Why it still matters
The Acqua Vergine water aqueduct carries the water to the Trevi Fountain, after having collected it 10 km (6.2 mi) from the Italian capital. The aqueduct is still in use today, despite some interventions during which the fountain remained empty. Calcium-free water is thought to be one of the causes.
Look closer
In 1629, Pope Urban VIII, finding the earlier fountain insufficiently dramatic, asked Gian Lorenzo Bernini to sketch possible renovations, but the project was abandoned when the Pope died. Though Bernini's project was never constructed, there are many Bernini touches in the fountain as it exists today. An early influential model by Pietro da Cortona, preserved in the Albertina, Vienna, also exists, as do various early 18th century sketches, most unsigned, as well as a project attributed to Nicola Michetti one attributed to Ferdinando Fuga and a French design by Edmé Bouchardon.