Edit Add: The retention walls are part of the kit. You have a fair amount of work creating the hill side. Here is a picture of the construction of the Cabin Creek model.
Takes some time, and a small band saw to cut parts. I was fortunate there were only two or three foundations to model. Small blocks of clear pine work well/painted.
Note that the model is modular, easy to move and work-on. I've always believed that a very good model foundation is a plus.
