I saw an ad on television recently that touted the importance of a good foundation. Just like the prototype, your model structures could be quickly and easily improved with a good foundation too. Look around at the buildings in your neighborhood; the foundations are usually visible as a narrow strip of concrete below the wall that makes up the side of a building. Sometimes the foundation is painted in the same color as the rest of the wall, sometimes it's left bare. Whatever its color, a quick box of styrene strip material will easily simulate such a foundation. If you don't add a foundation, you could end up with something like this image where the structure appears to be floating above the ground.