Exact opposite in perspective to the Giant Hole in the Ground illusion in Stockholm, Sweden, this particular one gives the illusion of height. Outside Paris City Hall an artist named François Abelanet made the illusion of giant grass ball which is actually flat. This land art covers an area of about 1500 square meters and it took 90 gardeners five days to erect this piece of art. The illusion doesn’t work from any viewpoint; you need to have a proper distance and a specific view angle to make it alive.
The art is actually a long rectangular patch of grass measuring 100 meters by 12 meters. When viewed from the right perspective, it forms a shape of 3D ball having a diameter of 12 meters. See the video below to appreciate how massive this land art is.