After testing the exterior of a house I'm building, I've found that a big honking mountain stands in the middle of my courtyard. Now, I've done all the necessary landscaping in the CK, and nothing shows up there. It doesn't seem to have collision either, seeing that I can walk right through it. So what's up with this mountain and how do I get rid of it?

In CK: http://img401.imageshack.us/img401/2092/asgardk.png
In game: http://img96.imageshack.us/img96/433/2013041300001z.jpg