I've filled in a huge cave with awesome cobblestone rooms, and have an extremely deep mine (bottom of the earth) that is very wide going straight down.
I've really only done this because i went into my mine and hit lava, i died, but didn't care because I would spawn in my bed and all my important stuff was in chests.
Then I realized that i had broke my bed, moved it and haven't slept in it yet...
Check it out if you want, but it's here so I can locate my house.