Mineral-rich waters originating from the Apennine Mountains of Italy flowed through ancient Rome's Anio Novus aqueduct and left behind a detailed rock record of past hydraulic conditions, researchers have said. Two studies characterizing layered limestone—called travertine—deposits within the Anio Novus are the first to document the occurrence of anti-gravity growth ripples and establish that these features lend clues to the history of ancient water conveyance and storage systems.