Check out this “moving forest” installation in Amsterdam:

‘Moving Forest’ is NL Architects’ answer to the lack of green in contemporary urban environments. One might occasionally find a carefully designed patch of plants or shrubbery there, but nothing like the majestic parks and shady trees that can be found in historical city centres. So they designed a park on wheels, with trees in shopping carts. Around a small street bench, the public can rearrange their own little park and thus create a nice green view and a bit of shade.

Via Matt Mechtley, who writes, “I see high potential for something like this combined with a flash mob. Move the whole forest across town!”