As I mentioned in the prequel rumours thread, my girlfriend's production company are currently filming in Spain, and the shoot happening next door to them is supposedly Prometheus. That is what they have been told, anyway. This came from a designer/builder who is working on their programme, who has also worked on the Spain Prometheus set, which he claims to contain a pyramid.
So there you go - I certainly trust Donna, but I can't say for sure about the people the information came to her from. An interesting tidbit, either way.
Sorry for cross posting, but it seemed relevant here.