I've been restoring this abandoned underground dungeon/castle and trying to colonize it. However, the colony deed keeps saying that it's unsuitable for tenants. I've looked everywhere for holes, I've run through every hallway and tried placing background blocks behind every foreground block, but still no tenants. It's a very large space so I'm thinking I just have one background block missing behind some walls that's messing things up. Is it possible at all to hide/make invisible the foreground? that way I'd be able to see for sure if it's because of something missing in the background as opposed to everything else. The building has doors, lights, and decor, and the foreground walls are sealed as far as I can tell.