Water-Powered Armillary Sphere and Tower

Song dynasty, Su Song and Han Gonglian, 1092 AD (replica)
Ancient Observatory Museum, Beijing

The incredibly sophisticated instrument shown here is a model of an ancient device, that combined the functions of a water-powered clock, armillary sphere, and celestial globe. Powered only by gravity in the form of falling water, and driven by a sophisticated gearing and escapement mechanism, it could both tell the time and model the ever-changing motion of the heavens.