For extrapolated environments I have firstly looked at Minecraft. Minecraft even though it is stylised to look blocky and pixelated, it does have areas that are based off areas found in real world. For example, forests, oceans, mountains etc.
There is a game that has used something that exists already and was changed in order to fit the genre of the game and also the style of it. It is Fall Out: New Vegas. As the name suggests the game is set in Las Vegas after a nuclear disaster.