Go
AKA
One of the most ancient and popular board games. Certainly dates back to period (and then some) in the orient; was starting to be discovered by the west late in period or a bit afterwards. I am not even going to try to list all the sites that give the rules to Go (there are, in all likelihood, tens of thousands of them), but here are one or two from an SCA viewpoint.
Variants
Reconstructions and Other Discussions