I’m not a programmer unfortunately… Are you looking for a way to construct landscapes with buildings inside of a three-dimensional videogame? There are world builder programs that don’t require programming, but I haven’t used them.
There is some information in Google:
Here is one example:
http://www.digi-element.com/wb/
Many games like Elder Scrolls have creation kits, but I don’t know if this lets you create landscapes and buildings:
I think that Portal II has a creation kit, but I haven’t tried it yet either. I posted a screenshot here: