Trevi, Rome: the Fountain, the Acqua Vergine and the Quirinal

Trevi's subject is water, and the water arrives by a Roman aqueduct. Roma Capitale records the Acquedotto Vergine under Rione: II - Trevi: inaugurated in 19 BC by Agrippa, drawing from the Agro Lucullano near the eighth mile of the via Collatina, at the modern locality of Salone, and running over 20 kilometres, predominantly underground, to end in the Campo Marzio. It feeds the monumental fountains of the Baroque city, among them the Fontana di Trevi, which in the modern age is its terminal mostra. Part of it is visible above ground in the rione: at via del Nazareno three partly buried travertine arches in rusticated blocks survive at the sides of a larger fornix, identified with the arch Claudius had raised to mark his victory over the Germans, above which is set the inscription recording his rebuilding of the aqueduct in AD 46. Roma Capitale describes those arches as part of the Acquedotto Vergine and states its rione as II - Trevi; no source we fetched places them in another rione.

The fountain itself is eighteenth-century civic architecture built against the façade of Palazzo Poli. Roma Capitale gives the authors as Nicola Salvi and Giuseppe Pannini and the dates as 1732-1762, in travertine, marble, plaster, stucco and metals, and records that Pannini concluded the construction, partly modifying the scogliera and regularising the central basins. It also records an earlier attempt: in 1640, for Urban VIII and in step with the enlargement of the square, Gian Lorenzo Bernini designed a fountain on the present orientation, of which only an exedra base and a basin were built, set against buildings later absorbed into Palazzo Poli.

Under the buildings on the far side of the same square, excavation at the end of the 1990s, during restructuring and consolidation work, uncovered traces of an insula of Neronian date fronting the Vicus Caprarius, converted partly into a patrician domus in the middle of the fourth century and partly into a large cistern collecting the Acqua Vergine. Remains of twelfth- and thirteenth-century buildings were found above and partly overlying them, and traces of that urbanisation survive in the medieval portico on the side of the square facing the fountain. The area has been reorganised and is open to visitors as La Città dell'Acqua.

The Palazzo del Quirinale was a papal residence from 1605 to 1870, a royal residence from 1871 to 1946, and has been the residence of the President of the Italian Republic since; the Italian Wikipedia article ties the two changes to the presa di Roma of 20 September 1870 and to the referendum of 2 June 1946. Its construction is not settled. One Italian Wikipedia article gives 1573-1583 with Ottaviano Mascherino as first architect; another says it was built in the years 1573-1585 by Martino Longhi il Vecchio and then, from 1578, by Ottaviano Mascherino. Sources differ, and this guide does not choose between them.

The square in front of it belongs to two rioni. The Italian Wikipedia article, citing Sergio Delli, Le strade di Roma, 3rd ed., Newton Compton, 1988, p. 809, places Piazza del Quirinale between Via del Quirinale and Via XXIV Maggio, nei rioni I Monti e II Trevi. From the Middle Ages and still into the nineteenth century it was known as Piazza di Monte Cavallo. The fountain and the obelisk standing in it are in Trevi: Roma Capitale states Rione: Trevi for the Fontana di Monte Cavallo, and records that in 1786 Pius VI had the Egyptian granite obelisk taken from the Mausoleum of Augustus in the Campo Marzio set between the Dioscuri, to a design by the architect Giovanni Antinori.

Buildings in Trevi appear in the Lateran Treaty of 1929 in three different ways, and the differences matter. Article 15 names the palazzi della Dataria among the buildings which, although forming part of the territory of the Italian State, enjoy the immunities that international law recognises for the seats of the diplomatic agents of foreign States: that is a diplomatic-headquarters immunity granted on Italian soil, not a piece of Vatican City and not a border. Article 14's third alinea instead transfers to the Holy See the ex-conventual buildings in Rome annexed to the Basilica dei Santi XII Apostoli, and Article 15 reaches only the properties indicated in Article 13 and in the first and second alinea of Article 14, so those buildings fall outside Article 15 altogether. Article 16 then provides that the properties named in the three preceding articles, together with the buildings used as the seats of a named list of pontifical institutes including the Università Gregoriana and the Istituto Biblico, shall never be subjected to encumbrances or to expropriation for reasons of public utility save by prior agreement with the Holy See, and shall be exempt from taxation, ordinary and extraordinary, whether to the State or to any other body. That is a property and tax provision. It is not extraterritoriality and it is not diplomatic immunity. The Gregoriana and the Biblicum both stand in rione Trevi, on Italian soil; neither is in Vatican City and neither is extraterritorial.

Trevi is bounded by streets rather than by anything you can see, and the Italian Wikipedia articles for the neighbouring rioni name them. Colonna's article gives its boundary with Trevi as piazza Barberini, via del Tritone, largo Chigi, piazza Colonna and via del Corso. Trevi's own article gives its boundary with Monti as via del Quirinale, piazza del Quirinale, via Ventiquattro Maggio and largo Magnanapoli. Via del Corso is crossed by four rioni and belongs to none of them; San Marcello al Corso and Palazzo Mancini are in Trevi while the Galleria Alberto Sordi, on the same street, is in Colonna.

Two of the rione's set pieces stand on ground shared with a neighbour. Piazza Barberini lies across Trevi, Colonna and Ludovisi, and Colonna's article names it as its boundary with Trevi. Piazza del Quirinale is shared with Monti. The buildings and fountains described here stand in Trevi even where their square does not.

At the fountain, Roma Capitale routes visitors in by the central staircase and out through the gate on the via dei Crociferi side, and caps the inner perimeter at about 400 people at a time; the charge, the free list and the hours are in the entry for the fountain below. For the aqueduct, entry is only to accompanied groups, by booking on 060608, and Roma Capitale states that the site is temporarily closed for works, so check before making the trip. We could not reach the Palazzo del Quirinale's own website from this network, and nothing here therefore describes whether or how the palace can be visited. The Accademia Nazionale di San Luca, the Gallerie Nazionali d'Arte Antica at Palazzo Barberini, the Galleria Colonna, the Scuderie del Quirinale, Palazzo Valentini and Vicus Caprarius each publish their own opening information on their own sites, and this guide sends you to those rather than repeating hours it could not verify.