Update: iOS 7 had this feature early on in the beta, but Apple seems to have removed it from the shipping version. No word on whether it will return, but it was still cool so I’ll leave it here for posterity and in the hope the feature returns.
It turns out that iOS 7 is anything but “flat.” Parts of it use a parallax effect to make it look like content can be underneath other content and move at different speeds, adding a sense of perspective and depth.
One of the many places Apple used this handy effect is on the completely redesigned iOS 7 lockscreen. As Cult of Mac shows in this Vine video, you can set a panorama as your lockscreen image, then turn your iPhone (and, presumably, iPad) around to move across the panorama.