British and Italian experts Friday revealed the chance discovery of the source of a 1,900-year-old Roman aqueduct complete with nymphaeum near the Italian capital.
"The existence of the aqueduct was known, but we thought it was from the medieval era," Edward O'Neill told AFP.
"Not only is it Roman, but it is from Trajan's time and we found its source," O'Neill said of the discovery some 40 kilometres (25 miles) north of Rome in June last year.
O'Neill, who was filming a documentary on Roman aqueducts with his father Michael at the time, teamed up with Italian ancient topography professor Lorenzo Quilici of the University of Bologna to authenticate the find.
Quilici, a foremost expert on Roman aqueducts, explained that the source of the aqueduct had been forgotten for centuries after the artificial waterway was partially diverted in the 16th century and said it was found in "extraordinary and adventurous circumstances."
A video compiled by the O'Neills captures the spirit in the title, "Roman Aqueduct Hunting in the 21st Century."
Culture ministry official Mario Lolli Ghetti underscored the site's "extraordinary interest given the state of conservation of the systems for capturing and filtering the water."
But much of the site is in urgent need of restoration.
Notably, it is threatened by the roots of a giant fig tree.
"We are documenting a crumbling treasure," said Michael O'Neill. "This unique Roman structure is being destroyed by neglect, and by aggressive fig tree roots."
Explore further: New branch added to European family tree