A repost from off-topic Altered Maps thread. what are these images showing? It's from the Medieval America site. The author is (was) trying to make a 'believable' world in which technology regressed back to the Middle Ages and America is a mish-mash of feudal kingdoms, nomadic steppe tribals, and absolutist hydraulic empires. This clearly is some geometric way of determining where (feudal?) nations/kingdoms would form, but how does it work? Clearly, the gold colour represents regions unsuitable for forest-zone agriculture. They separate other regions, which are more suitable. In the first picture, we have Europe and the same methodology is obviously applied in the second map. This would explain his other map: Spoiler : So, any ideas? Do you think it is a legitimate method developed by "historians" (probably those dealing with history on the most general level, like Jared Diamond), or the author's own idea? He also mentions another method for determining the "litoral" regions where maritime civilizations are likely to arise: This leads me to think the methods from the maps above may also be taken from somewhere else. Anybody knows...?