About an hour spent on a train away to the south-east of Paris will land you in la Forêt de Fontainebleau. It weighs in at two and a half times the size of the city proper and is immeasurably more beautiful.

The forest is known for its curious rocks, which are believed to have formed naturally and resemble all sorts of animals, such as elephants, tortoises and crocodiles.

More than that, though, there are over three thousand species of mushrooms that have been discovered throughout, two thousand species of animals and five thousand of insects.

So it seems to have Paris beat on population density as well.