Thanks to Karl Donert for the reminder of this post on the Google Earth blog which describes the "little planets" created by Janis Petke.
There's an example shown below, of London. I love these. There are some instructions for how to go about making your own, but I guess they take quite a long time. I have an app which produces a similar effect, but nowhere near as detailed and crisp as these.
Images made by Janis Petke