Vicus Caprarius, the Trevi Underground

Few visitors who squeeze toward the Trevi Fountain know that a Roman street, a block of houses and a huge water tank lie underneath the buildings beside it. The site, known as Vicus Caprarius or the Water City, was found during building work in the 1990s and now lets you descend below the modern city to walk among the walls of Roman dwellings, a section of ancient paving and the cistern that held water for the neighborhood. The link to the fountain above is direct: the Trevi is the terminal of the Aqua Virgo, an aqueduct that Agrippa built in the first century BC, and the water still arrives on the same line. The partner listing places the site in Piazza di Trevi and shows it open Tuesday to Sunday from late morning to mid-afternoon, closed on Mondays, with a range of ticket options from a plain entry to short guided tours of the underground domus of around forty to forty-five minutes and longer walking tours that include the area. The booking page does not make clear which options include entry, so read each option before you pay.

Why go? Because it makes Rome's layering physical. At street level you are among Baroque palaces and souvenir stalls; below, you are looking at brick and stone from a Roman apartment block with a water system and a cistern, and the contrast is the point. The site is small and compact, which makes it an easy add-on rather than a half-day commitment, and its low-key setting offers a calm break from the throng at the fountain only a few steps away.

It is not a spectacular ruin; it is an atmospheric, human-scale one, and it rewards curiosity more than a quick look.

The guided tours are worth the small extra over a plain entry, since the walls and channels mean little without explanation. The booking page mentions guides in several languages and small groups of around twelve for the shorter tours, though group size and language depend on the option, so check the details on the date you want.

Expect stairs down and a cool, slightly damp atmosphere; bring a light layer even in summer. Opening hours are limited, so plan the visit around them instead of assuming the site is open all day. Children generally like the idea of a hidden Roman house under a famous fountain.

The houses here were abandoned, flooded, buried and eventually built over, and the cistern was used for centuries as a source of water for the neighborhood before the modern streets closed over it. When you come back up to the piazza and see the fountain's water pouring into its basin, the line from ancient aqueduct to Baroque showpiece is easy to see, and that is the real value of the stop.