For those who don't know about it and are interested in photography of old London Town this is a must have for the smartphone!
The app has hundreds of photos of old buildings and streets in its database, and is GPS enabled.
The reason for GPS is that if you are near a spot in London where the app has an old photo of the street that you are on, you can bring it up on split screen, whilst also being able to see your own view through your camera.
So you can overlay the two and try to match the past with the present.
I can't get enough of it and is probably the closest that I'll get to Jules Verne & time-travel - in my head anyway.