Near the town of Gallicano nel Lazio there is a massive structure, ancient, unmapped, and unknown to the casual hiker, even though it’s just a short walk from the Via Polense that connects Rome with Poli. The ruins of the aqueduct, which date from the second century B.C., are located in the Tenuta di San Giovanni in Campo Orazio, which is one of the locations where a famous fight between the Horatii and Curiatii (a story from the early days of Roman history) is believed to have taken place. The…