I had somehow ended up with a big cavity in the ground under my house. Having a big underground room has been a long-standing dream of mine, but this one was so large that I worried it could collapse. The walls and floor were mostly just gravel! It was a very irregular shape, with multiple openings to the outside around the edges, and a large, maybe 15-foot high space in the middle. The topology was further complicated by a second, mostly-separate underground cavity, which in turn connected to a network of secret crawl spaces throughout the house, which I had discovered years ago (this was, I think, inspired by a dream about secret passageways through my parents' house that I had years ago; assuming I wrote about it, a link to that entry would be appropriate, here).

The two cavities may have intersected in one small space, but otherwise managed to twist around each other and my actual house in such a way that it was not obvious which one was over or under the other. Confusing, but awesome.

I decided that a good way to put this cavity to use would be to fill it with cat my litter bins full of sawdust. I could stack them to build columns to brace the walls and ceiling while simultaneously de-cluttering my house!

See also: this dream about a big dirt room under Joh's basement.