You may already have noticed them in Paris or elsewhere; those little retro video game-style aliens placed on the walls of buildings by the street artist called Invader. Currently, 3589 Invaders have invaded the world, including 1357 in Paris.
Download the Flash Invaders app (available on the AppStore and Google Play) and go search them out all over Paris. Collect points as you locate each invader and try to beat the highest scores.
An original way to discover both Paris and street art!
Website: http://space-invaders.com/flashinvaders/