Fontana dell'Acqua Paola

Where it sits. The Fontana dell'Acqua Paola stands on Via Garibaldi, part way up the Janiculum hill above Trastevere, facing east across the whole of Rome. Romans call it il Fontanone, the big fountain, and the name is fair: it is a marble and travertine wall about the width of a small church façade, with five arched niches pouring water into a single great basin. The terrace directly opposite is one of the most reliable panoramas in the city, taking in the domes of the centre, the Vittoriano, the Alban hills on a clear day, and — from a few metres further along the road — the dome of Saint Peter's.

The story behind it. Paul V, of the Borghese family, restored a ruined ancient aqueduct that drew water from the area of Lake Bracciano, roughly forty kilometres northwest, and this fountain was built between 1610 and 1612 as its ceremonial outlet. Giovanni Fontana and Flaminio Ponzio designed it, taking the earlier Fontana dell'Acqua Felice as a model but enlarging every element. The materials tell a Roman story of reuse: marble was taken from the Temple of Minerva in the Forum of Nerva, and six columns of red granite came from the façade of the old Constantinian basilica of Saint Peter, demolished to make way for the present one. The composition originally emptied into five separate small basins; Carlo Fontana replaced them in 1690 with the single wide basin seen today, which is what gives the fountain its sheet of falling water rather than five thin jets. Borghese eagles and dragons run across the attic beside a self-congratulatory inscription.

On screen. The fountain opens Paolo Sorrentino's The Great Beauty (2013), and the sequence is worth describing precisely because it is so often misremembered. A choir stands in front of the basin singing a piece by the American composer David Lang; a group of Japanese tourists photographs the panorama from the terrace opposite; one of them lowers his camera, turns, and collapses. Only then does the film cut to Jep Gambardella's birthday party. Sorrentino uses the Janiculum exactly as Rome uses it — as the place where the city is looked at from outside itself — and the tension between the ceremonial water wall and the sudden, unexplained death sets the film's terms in under four minutes. The same terrace and the same stretch of Via Garibaldi appear across Italian cinema and television whenever a scene calls for a character to stand above Rome and think.

What the water was for. The restored aqueduct was not built for display. Its flow was heavy enough to drive a line of flour mills strung down the Janiculum slope towards Trastevere, and it supplied the fountains of Saint Peter's Square, the Vatican gardens and much of the right bank of the Tiber, which until then had depended on wells and the river itself. Roman wits complained that the architects had produced an enormous frame for a modest quantity of water, and the criticism stuck long enough to be quoted in guidebooks two centuries later. The basin is fed continuously and the overflow runs to a grille at the foot of the wall, so the sound in the small piazza is constant and loud enough to blot out the traffic climbing Via Garibaldi behind it.

What else is on the hill. The Janiculum is not one of the seven hills of ancient Rome and it was never densely built, which is why so much of it is park. A few minutes north along the ridge is Piazzale Giuseppe Garibaldi, with the equestrian monument to Garibaldi and the ranks of busts of the volunteers who fought the French in 1849; a cannon is fired there at noon every day, a signal for the city's clocks that has been kept up since 1847. Just below the fountain stands San Pietro in Montorio with Bramante's Tempietto in its courtyard, a small circular chapel of 1502 that is one of the pivotal buildings of the High Renaissance. The Orto Botanico, Rome's botanical garden, spreads down the slope towards Trastevere.

Getting there and timing. The walk up from Piazza Trilussa in Trastevere takes fifteen to twenty minutes on a steep, stepped path and comes out beside the fountain; buses 115 and 870 climb the hill for those who would rather not. There is no ticket and no gate. The fountain faces east, so it is lit by the morning sun and falls into shadow in the afternoon, while the panorama behind is at its best in the hour before sunset when the light is on the domes. Evenings are lively: the terrace fills with Romans, and parked scooters line the parapet. Late morning on a weekday is the quietest time to see the water wall itself without a wedding party in front of it — this is one of the most heavily booked wedding photography spots in Rome.