Paris' Weirdest Park
Built on top of the site of a former Citroën manufacturing plant, Parc André Citroën is a unique concept park space. On the site of the former plant are six "Serial Gardens" were designed to associate with a day of the week, an element, a metal, a body of water, and a sense. A Garden of Movement, where plants grow wild and free. Two greenhouses stuffed with exotic vegetation. Both "white" and "black" gardens, designed to suit the moody whims of you, the mercurial visitor. Even a moored hot-air balloon, which you can enter for a little bob up in the air and then come right back down (for a fee of 12€ on a weekend).
This park, in the 15th Arrondissement of Paris, is one of my favorite places in the city.