So, a calendar...
Well, a calendar that can predict the motion of the sun, moon and planets. 200 years before Christ.
The link in post 2 is pretty interesting and goes into a lot of detail in why the device was important. Lots of people back then referred to the technology, and it is believed that many of these devices were made and used back then. For some reason I always thought this was such a mysterious thing and that it was one-of-a-kind.