We recently published a photo of one such gathering, at the Museo della Civilta', amid the enormous columns of Mussolini's EUR. In this one, we're at Parco degli Aquedotti (Park of the Aqueducts), with our teens displayed along one of the park's aqueducts, low here because it's going to ground at this point (toward right), soon to be fully underground.
The name of this aqueduct is Acqua Felice. Though not of ancient origin, it's old enough (Hillary), constructed in the late 16th century under Pope Sixtus V. The Parco is fully described in Itinerary 1 in Rome the Second Time, along with a good story about Sixtus (not the nicest man) and Acqua Felice, which didn't work right when it was turned on. Those teens in the photo probably don't know the story, but they're making good use of the structure, which still carries water to Rome.
And here's a link to a Google Maps version of Itinerary 1's map:
http://maps.google.com/maps/ms?ie=UTF8&hq=&hnear=Rome,+Lazio,+Italy&msa=0&msid=115234173574934358486.00048bfd318d41d8b7cb1&z=15 Google Maps versions of all 16 maps in the Book (accessible by hyperlinks in the ebook versions) are in a document at right (under the Book Updates document), also available by this link: http://www.scribd.com/doc/56172132/Google-Maps-Versions-to-Rome-the-Second-Time-book-maps