A paper on the Mechanism appears in tomorrow’s Nature. In brief what it is these days is a rather unimpressive looking lump of heavily corroded metal. I have a photo of it somewhere, but it’s a very bad blurry photo which doesn’t do justice to its lumpy unimpressiveness. Fortunately Wikipedia has this much better photo.
The Antikythera Mechanism in the National Museum, Athens. Photo from Wikipedia.
The reason why it’s news is that there’s been a lot of painstaking work to try and see beyond the corrosion, and its proven spectacularly successful. The mechanism has been examined using X-ray tomography, which is where X-rays are used to build up a cross-section of a subject slice by slice without physically pulling the subject apart. The results are confirming that Greek technology could be staggeringly sophisticated.