When we first got the trampoline, we just stuck in on the corner of the weed patch.
We hired someone to dig a pit for us, and I rounded it, flattened it, and built the retaining walls.
When the trampoline was done, we no longer had a weed patch, but a mound of dirt. This we had flattened out, as we weren't sure what we were going to do with it yet. Looking at this raised region of dirt, my wife began to envision a hill sort of "growing" up from it. And then she realized, "Hey, if we are going to put in a hill, why not make it into a hobbit-hole?"
You may be wondering about now how a person can look at a dirt patch like this, raised only about a foot and a half above ground-level and think hobbit-hole, but you don't know my wife....