VICOVARO, ITALY—Speleo-archaeologists are using GPS technology, remote control robots, and laser rangefinders to update the maps of Rome’s 11 ancient aqueducts that were compiled between 1906 and 1925 by British archaeologist Thomas Ashby. The carefully engineered aqueducts used gravity to carry clean water into the city. “Water was a fundamental service for hygiene. In a city like Rome, which had a million inhabitants, there were very few epidemics,” said Riccardo Paolucci of the group Underground Rome.