It will be large enough, as developers we will not put any restraints similar to Sim City in regards to the map’s size and so you’ll have a big sandbox and we could of course implement the possibility of buying more land if needed. However, we will issue “recommendations” or perhaps guidelines as to what amounts of simulated agents the game can push out on an average computer at an acceptable FPS. We currently do not know what these amounts are since there is still loads of optimization and testing left to be done!
In regards to different terrains, water is indeed possible, mountains or very much so elevated terrains is a bit more tricky (in regards to how it would perform or be interpreted from a gameplay perspective). Initially I’d say water, yes, elevated or rough terrains, no.