I love nothing more that a tramp round a city. Taking the Metro in Paris is very simple - and fairly cheap - but the riches you discover wandering around make up for the extra time needed.
A few years ago, Miss Geeky introduced me to Space Invader spotting.
Before I went to Paris, I had no idea that there were any Space Invaders lurking on street corners. I've since realised that it's possible to get fairly detailed maps of where the invaders are. Or rather, where they are supposed to be - they have a habit of moving. Or, more likely, being stolen!
For me, running around the city specifically looking for the little blighters ruins the sheer joy of finding them by chance. We spotted nine in total - one of which was on the banks of the Seine, but our boat moved too quickly for me to capture it.
Here are photos of the ones that I found. Annoyingly, my Nexus One didn't geo-tag the images - hopefully the street signs should give you a clue as to where they can be found.
So, next time you're in a big city - keep watching the skies!