This anachronistic piece of technology was unearthed in what's now Iraq in 1838. There isn't just one so-called 'Baghdad Battery,' there was a whole series of them! They're a set of clay jars containing iron rods wrapped in copper, and they date back over 2200 years.
Wilhelm Konig, who found the batteries, had his archaeology students re-create the batteries under test conditions. They worked - they were capable of generating an electrical current. How and why were people creating these modern tools thousands of years ago?