This one happens to be in my backyard, so I may have to check it out later.

Down in Greenwich Village, there is a giant sculpture of a cube, which has been there since it was installed in 1967. Apparently, it has been a target for pranks several times before, including one that turned it into a Rubik's Cube.

Well, this morning it has been turned into a giant Companion Cube, straight from Portal. Someone took the time to basically make a cover for it ot of fabric, which actually looks pretty authentic. Caltec's Prank Club is claiming to be the masterminds, or so we assume based on a note found at the scene.

[kotaku]