Please, if you have no time to waste, don't read any further, because this is addictive!!
GeoGuessr - Let's explore the world!
It is an online game using Google Streetview, which drops you in some unknown place and you have to work out from any clues you can see - street signs, scenery, guesswork - where you are. You score points for how close you get.
Utterly pointless, utterly addictive. But lots of fun. You have been warned!! :)