The ancient version of battery

 This is easily one of the more controversial ancient inventions on this list. Even more so, the ancient device was stolen in 2003 and has yet to be found. As its name implies, the

Baghdad Battery, also known as the Parthian Battery, is a 2,000-year-old ancient artifact that could be an ancient version of a battery. The ancient invention was discovered in 1983 by a German archaeologist in Khujut Rabu, an area right outside of Baghdad.

Inside the clay jar, you will find a copper cylinder and iron rod. If you were to pour a weak acid into the clay jar, something like vinegar or even grape juice, the combination would cause the "battery" to generate about 1 volt of electricity. However, why would an ancient civilization need a battery? 

At the moment, that is unclear. In fact, to this day, archeologists have only found one battery. Even more so, there is no written record describing the exact function of the jar.