I'm playing the latest installment of the Tomb Raider, where you uncover secrets of ancient Incas and Maya. The game is full of huge stone doors that open only when you go through an elaborate sequence and so on. It's pretty obvious to me that what's portrayed in the game is an artistic exaggeration, but it led me to wondering about the elaborate mechanisms that did in fact exist. Now, I'm mostly interested in large and even gigantic mechanisms, but if you have anything interesting of the Antikythera's size, feel free to share too.
One has to distinguish the things for which we have direct archaeological evidence, the things which can be reliably reconstructed from literature sources, and the things which are mentioned in the literature but with inadequate description such that we have no idea how they really looked.
To the first type belongs the Antikythera mechanism.
Examples of second kind are artillery pieces, and various machines described in the book of Heron.
All these things belong to the Hellenistic epoch.