I just watched Ancient Discoveries on History Channel about China. They skipped some of the obvious Chinese discoveries---paper, printing, silk, gunpowder, rocketry, and went to really mind blowing stuff that you would think that ancient people would not have invented at all.
For example, in the Han Dynasty, they showed that someone actually invented the Seismograph. Yes, something that could detect earthquakes from a distance and even point to the direction of its origin. Interestingly it uses the same principles modern seismographs did.
Another is the invention of the Odometer. Though the Chinese actually called it the Range finding Chariot. You have a cart that is basically designed with a reverse transmission set of reduction gears connected to the axle, and the reduction gears are connected to a pair of moving mannequins by cranks. At every 500 meters, the mechanical mannequins would ring a bell. The rangefinding chariot is used with army marches to accurately tell the distance of the marches.
Some of these ancient inventions are not found buried in the ground but are still working in the rural countryside in China.
Among them is an early design of an oil rig which allows ancient (and rural) Chinese to bore through the ground to get to oil deposits. The rigs uses a set of interchangeable drill heads, each optimized to drill against a certain rock layer type.
They showed a working automated pounding hammer machine. Ancient but still working in the countryside. The water wheel turns a center rod. The rod acts like a cam which has lugs of various deliberate lengths. The lugs in turn act upon a series of hammers, which is used to pound various grains automatically.
They also showed another ancient rural machine still working that is used grind grain. A water wheel powers a set of gears that turns various millets.
They showed an ancient piece of jade whose complex spiral pattern could only have been done by a precision compound machine.
From texts they showed various designs of water wheel powered automatic bellows machines that blow air into blast furnaces into an industrial scale.
The Terra Cotta army all shows signs of industrialized mass production. One of the treasures found is the Emperor's Chariot, which is made of 3600 pieces that are casted individually. To be to pierce together something made from thousands of pieces that are casted confidentially and independently from different sources means an understanding of the mass production process that includes strict defining of specifications. Furthermore, each piece is then welded together to form the chariot.
To produce the army, each soldier weighing at least 300lbs, very well crafted and armed with metal weaponry, requires a civilization that has a true industrial base. Meaning vast kilns that churn out the statues like factories, and vast factory like blast furnaces that churn out the weapons and armor.
Many of the weapons like swords, still retain their original lustre and hardness, which means they can still kill today. Later they found out that many of the weapons have a thin trace layers of chromium oxide. Yet Chromium isn't used in steel to increase hardness and resist corrosion until the 20th Century. Long time ago, these people knew not only how to make and forge steel but understood well enough of the use of chromium to improve it.
Sometime in the Sung Dynasty, someone invented what is mankind's most complex device yet until the Industrial Age. It was called the Cosmic Engine. The machine itself was used through out the time span of the Sung Dynasty until it was destroyed when the Dynasty itself was destroyed. But even destroyed, the inventor left complete documentation of its creation, mechanical principle, and blueprint, and a working replica was made from the blueprints.
Basically the machine itself is like 5 story mechanical clock, complete with gears, chain drive and an escapement mechanism, that rationalizes the use of mechanical energy in very precise amounts. The machine was meant not just to keep time, but keep tabs of months, seasons and even years, and inside it has an armillary sphere and a mechanical celestial globe that is used to track the movements of heavenly bodies precisely.