It's easy to think of the evolution of technology as a linear process, starting from the most primitive simple machines and only improving up to the self-driving cars and artificial intelligence that we have today. But that's not quite right. Some ancient cultures managed to develop some bafflingly complex and sophisticated inventions using techniques and knowledge that seemed to come out of nowhere, and in some cases weren't replicated for hundreds of years afterwards. Scientists and historians are always working hard to figure out how these inventions came about, but some secrets are hidden in history forever. Intrigued? Read on to uncover impressive ancient inventions.