To do so you would need to make the polygons double sided.
Normally (no pun intended) the polygons of a building you are in, face inward, so when viewed from outside they disappear.
You can make them double sided (in fact I think there is a key for that in Decorator, can't remember exactly now. The readme.txt file should tell you), but that would only make the outside look the same as the inside. Other than that, you would need to make a polygon representation of the outside and place that over the top of the 'Interior' mesh.
Normally (no pun intended) the polygons of a building you are in, face inward, so when viewed from outside they disappear.
You can make them double sided (in fact I think there is a key for that in Decorator, can't remember exactly now. The readme.txt file should tell you), but that would only make the outside look the same as the inside. Other than that, you would need to make a polygon representation of the outside and place that over the top of the 'Interior' mesh.