Jerome Grasdyke posted this info about map-making ages ago:
A few other caveats about regions:
- they should be 'convex' (one landmass, no inaccessible areas)*- they should have only one settlement and only one port
- all land tiles should be part of a known region
- each non-sea region should contain at least some fertile tiles
- continuous sea surfaces should form one region
- the maximum number of regions supported is 200
- the distance between the centres of any two adjacent regions should not exceed 50 tiles*
*: not doing these things shouldn't cause a crash, but it may cause the AI to mess up.
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