Here is what my wife wrote about it in our family newsletter, in her own words:
So, how do you make a hobbit-hole, which everyone knows must have round walls? We finally settled on a large-diameter pipe for the structure. We found out from a nice neighbor who deals in large-diameter pipe that the one we'd need is around $1500. OK, maybe dreams are dreams for a reason. So we looked around for a nice used pipe (anybody got a 6-foot diameter pipe lying around?) all the while praying (yes, praying) that we could find something for a better deal. Just as we were deciding to bite the big $1500, our nice neighbor called me up and asked if we'd gotten our pipe yet. "No," I said. "We're looking at our options right now." "Well," he said, "I was walking around my yard the other day and there was a 6-foot diameter pipe!" In your yard? I thought. "You're kidding," I said. Then it dawned on me: his workyard! He wasn't kidding! He said, "I don't need it, so if you want it, I'll sell it to you for 50% cost."
Oh, boy! God does want us to be happy! So I got on the phone with our next-door neighbor, to ask if we could drive a flatbed trailer and crane over their lot to get the pipe into our yard. "Oh!" he said, "we're grading our backyard for sod tomorrow." Thud, went my heart. "But if you can skirt around the edge, I don't mind you doing it, he added." "Oh, thanks! You're an angel! I don't know how we're going to 'skirt' with a flatbed and crane, but we'll sure try." Well, the next morning my large-diameter pipe neighbor called and said, "We've got time to deliver the pipe this morning." Thump, thump, thump, went my heart. "Really! OK." So they brought the pipe across the weed patch and I'll never know if you can actually 'skirt' with a flatbed and crane.
As they lifted the thing into place, my phone rang. "Hello? This is your back neighbor," (who I've never heard from and don't even know her name). "I'm just curious what you're putting in your back yard?" Suspicion laced her voice, like she thought we were installing the mother of all drains, or a highway culvert. I toyed with the idea of leading her along, but since I don't know her and since she is likely to be my neighbor for the rest of my life, I just told her the truth: we thought a hill with a tunnel under it would be fun for the kids. She was pretty relieved, but I believe I could see her face in the window the whole time they positioned the pipe.
The next week our weed-patch-now-graded-for-sod neighbor called to ask if we wanted the pile of dirt from his yard to cover our pipe. "The guy can just dump it right over the fence for you," he suggested. Well! That beats wheeling it around the house barrowful by barrowful! So we got free dirt dumped almost right where we wanted it! So now we just need to hire a backhoe to get the dirt right where we need it, figure out sprinklers, sod it, and we've got a hill for sledding and water sliding, and the structure of our hobbit hole.
Well, let's just say there was a bit more to it than that...