The Air In the Ampule Room

The air in the ampule room is breathe-able, there's no radiation, it's at room temperature and the gravity seems the same as Earth's. We have seen evidence of that in the trailer and the stills. Why is this? I think the ampule room was readied in anticipation of our arrival. Not to mention the presence of a giant human head statue. Why would an alien race travel with such dead weight? I'm beginning to think that the Ampule Room is in an alien temple on the Engineer's world. The space jockey ships we've seen are separate from the Ampule Room altogether. Is there a thread which already discusses this idea?