The Antikythera Mechanism is a really interesting piece of ancient technology, it is one of the most sophisticated scientific instruments that has been found from antiquity to date. It was an analogue astronomical computer with inscriptions from the zodiac, months of the year, and also the planets. Mechanically it is quite complex with over 30 precision bronze gears, which also include a differential gear.
Discovered by sponge-divers on an ancient shipwreck off the island of Antikythera in 1901, it has be suggested that it was built in Rhodes in about 80 BCE however other more recent research push that date back to 200BCE. What is really significant is that it shows that advanced technologies we present in Antiquity and were later lost until they were being re-invented some 1500 years later. It only makes you wonder how many other pieces of ancient technology are still left to be discovered.
The Antikythera mechanism is now located in the Athens, at the National Archaeological Museum.