Appear out of Nowhere!

I always wonder how and where giant cranes come from. One day everything's normal in the sky and then BAM the next morning there's a 100 foot crane towering in the sky. It's like they appear out of nowhere! I always wondered how they get there. Do they drive? Cause I've never seen one going down the road (and I don't think they'd fit under overpasses. And they don't look like they shrink down; so how do they get to their destination and then one day after their job is done vanish again!?