Mother of all terrain modeling questions

[eidsvolling]

I have an outlandish ambition to model a particular railway engineering feat in mountainous terrain. Does anyone know of a way to model terrain from contour line data sets (preferably in HO scale)? My thought is to build a framework from the contour lines and build out the finished surfaces on it. (I know how to locate sources for such data sets.)

Any blurting out of a correct guess as to the location will be deemed as volunteering to help with the project.