Apple software engineer Andrew Carol built a fully-functional replica of the Antikythera Mechanism, the world's oldest known scientific computer. The 2000-year-old analog device was used by the ancient Greeks to predict the year, date, and time of future solar and lunar eclipses accurately to within two hours. Carol put together the 110 gears (made with 1,500 LEGO Technic parts) in just 30 days. See how it works below.
For more information, check out Fast Company's interview with Carol.