Eclectic worldbuilding

 - It always struck me that Greyhawk was a setting which allowed Gygax to pitch troops of different historical periods against each other.

- I used to consider this a weakness, but then I heard an interview with the lead designer of Pathfinder, who said they made Golarion as "a world to have adventures in".

- Then I wondered if this was the right approach after all, it is certainly what The Dark Eye authors did with their Aventurien setting, right down to the name.

- After all RPG settings are primarily places for PCs to do things.