At Astor Place, on the Lower East Side of Manhattan sits a large black cube sculpture. Installed in 1968, the cube can actually be spun upon its axis, when you get enough people. The place is a hangout for gothic-types, NYU students, and is seen daily by thousands of riders on the 6 Train.
And someone enterprising folks, one day in 2003, decided to turn it into a giant 3x3 Rubik's Cube.
By creating 54 cardboard panels, and duct taping them to the Astor Place cube in the early morning, they created a wonderful piece of pop art out of another piece of modern art. However, this was only temporary. At 8 PM, the NYC Maintance Department powerwashed off the cardboard panels. The Rubik's Cube was no more.
For more information, pictures, and things, visit http://www.alltooflat.com/pranks/cube/ - the site of those responsible for the prank. I'm not part of it, just a reporter.