Ancient Computers
The Antikythera mechanism is an artifact discovered in an ancient shipwreck in 1901, believed to have been built between 200 BCE and 87 BCE, and lost at sea between about 70-60 BCE.
Some remarkable efforts in recent years to recreate a model of the mechanism are nicely summed up in this paper. From highly detailed three-dimensional X-Ray images the authors were able to decipher the gear ratios used to determine the epicycles from text hidden within the machine. They then constructed 3D computer models and a working version of the machine from brass.
A Model of the Cosmos in the ancient Greek Antikythera Mechanism Nature Scientific Reports, 12 March 2021
The accompanying video is fascinating