When in Paris...

...There was an event in front of the Hôtel de Ville de Paris informing people about community gardening, specifically a concept called Keyhole Gardening, a form of permaculture.

The basic concept is to have a round-ish spot of soil with a hole in the middle, which serves as a compost and therefore will give nutrients and humidity to the soil for the plants, herbs, veggies to grow around it.