I would like to generate a relief map of a portion of imaginary world which would be about the size of Europe. I do not want to define the outline of land masses or bathymetry myself; I want the system to do that automatically, kind of like the way Civilization generates random world maps. I would like to define the balance of land mass versus ocean, and also the ratio of islands to continents (Civilization also does this). It would be an added bonus if the system could draw country boundaries.
What would be the best way to do something like this?