It's not just a crack on the wall. "Find the cracks and exploit the discoveries to be revealed there . then move on to practice running headlong into the brick walls. Cracks crack first. Heads crack before brick walls. (from: STREET ART UTOPIA)"
Argentinian artist Leandro Erlich created this illusion of people walking underwater called The Swimming Pool, for The Century Museum of Contemporary Art in Kanazawa, Japan. It's a piece of glass with water on top of it, and empty space on the bottom.
Geometric Street Art By Aakash Nihalani Brooklyn-based artist Aakash Nihalani embellishes the urban landscape with his fluorescent geometric shapes that float in midair and cut through buildings, skewing the perspective and disorienting the viewer.