I'm trying to build a piece of terrain about 10 miles long... I'm planning to populate it with buildings, flora, and people, so I want the scale to be such that I can really get in there.

Is this unreasonable? Or rather, if I started out with 1 of those units of terrain, is THAT a dumb way to go?

In the end, will it make more sense to use 1 unit to get the overall shape and then fake specific shots with bits and pieces built for those specific camera angles?

I know this is all kind of vague... I have no clue as to what I'm doing, just learning this program, if it isn't obvious...

Any suggestion greatly appreciated.