Rome had a vast system of aqueducts, but residents of a distant outpost like Londiniumthe Roman name for Londonhad to draw their water from local springs and streams. Or so historians believed, until a team from the Museum of London Archaeology Service uncovered the remains of three giant water-lifting systems. One device found near the heart of the ancient city could have raised 37,500 gallons a day using a chain to pull buckets up from a deep source. "They were most likely driven by a slave walking on a circular treadwheel," says Ian Blair, the archaeologist who led the dig. The water was most likely dumped into collection tanks and diverted along channels or through a primitive pipe system. "The Romans brought with them the culture of bathhouses and high standards for clean water," says Blair. Londinium's wheel-driven lift dates to the first century A.D., by which time local waters were already quite dirty. "Then, as now, streams and the Thames were the dumping ground for liquid waste. It's probable that pollution was so bad that these wheels were an important source of fresh water," Blair says.