Trevi Fountain

The largest and one of the most famous fountains in Rome

The Trevi Fountain (Italian: Fontana di Trevi) is a fountain in the Trevi district in Rome, Italy, designed by Italian architect Nicola Salvi and completed by Giuseppe Pannini and several others. Standing 26.3 metres (86 ft) high and 49.15 metres (161.3 ft) wide, it is the largest Baroque fountain in the city and one of the most famous fountains in the world.

The fountain at the junction of three roads (tre vie) marks the terminal point[4] 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.
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As for Nicola Salvi's project drawings

Nicola Salvi (Rome 1697-1751), Project for the Trevi Fountain: front elevation, 1733, pen, brown ink and black pencil, watercolor in gray and bistre, 397x557 mm

It is perhaps one of the most representative drawings of the collection kept in the Municipal Cabinet of Prints: it concerns the final project for the Exhibition of the Virgin Water in Piazza di Trevi executed by the architect Nicola Salvi, academician of San Luca, architect of the Sacred Apostolic Palaces and the Archconfraternity of Oration and Death. The project won the competition announced by Clement XII in 1732 and Salvi dedicated most of his activity to the creation of the fountain. The Aqua Vergine aqueduct, which ended at the Pantheon, was carried on to Piazza di Trevi by Urban VIII and many architects, including Bernini and Pietro da Cortona, tried their hand at trying to refurbish the fountain. In 1731 a first competition was launched which had no winner. For the 1932 competition there are three other drawings by Salvi, known from the descriptions of the Militia and the architect himself: the one reproduced here, which already represents the final project, is not a presentation drawing, but a used worksheet. probably by Salvi to define the development of the sculptural elements of the complex. The feature that distinguishes the fountain, one of the best known and most significant of the Roman constructions of the first half of the eighteenth century, is the relationship between the architectural structures of the Poli palace that acts as a backdrop and the perfectly interacting sculptural decoration. The statues, the cliff and the figures on the first floor descend from the greatest Roman Baroque tradition. In the niches on the right and on the left there are the Fertilitas and the Salubritas, while the central statue of the Ocean on a chariot pulled by sea horses made in 1762 by Pietro Bracci belongs to a subsequent execution; finally, the depictions of the four seasons appear on the attic. At the Museum of Rome there is also a large wooden model of the Trevi fountain carved and painted by Camporese in 1735, taken from the drawing by Salvi.
Source: http://www.artleo.it/