"Considering their time, layout and unearthed relics, we believe the three moats probably existed and functioned during the same time, but were different in their usage. The outer two were for defense and water drainage, but the inner one was a ditch-like production and living area," says Guo.

"The moat system was a major project accomplished after careful plan and measurement. It was mainly used during the early stage of Majiayao culture, about 5,000 years ago as the country's earliest known multi-rectangular moat structure and may be a prototype of oblong (or square) cities (that appeared often in later dynasties)."