When the Disney-MGM Studios opened, the Imagineers created one of the world's largest Hidden Mickeys of all time. This was a true Hidden Mickey, since you could only see it from high above.
Take a close look at the Disney-MGM park map above. See the white and light gray space in the middle?
Now let's flip it around and zoom in a little. See the face a little more clearly?
I found the following shot on the web a few years ago and, sadly, I can't remember where I got it. It is a great shot of how the Mickey used to look before the addition of the Sorcerer's Hat and the expansion of Sunset Boulevard.
I'm always preaching to look up, but sometimes it pays to look down!
If you want to see more hidden details of Disney's hollywood Studios, then check out the fantastic The Imagineering Field Guide to Disney's Hollywood Studios by Alex Wright.