"We got up there and I looked over and people had signed... I went, 'Well, no one can see it; it's so high, so I crawled over the side and signed some messages to (wife) Kate (Holmes) and the kids." Tom Cruise has left his mark at the very top of the world's tallest building. The action man scaled the Burj Khalifa in Dubai for sky-high scenes in new movie Mission: Impossible - Ghost Protocol.