Maybe some city really did sponsor the urban art project depicted below. But I doubt it. It definitely looks photoshopped to me. There must be an original David-free version of this picture floating around somewhere.
Update: The fountain is real. It's the Crown Fountain designed by artist Jaume Plensa in Chicago's Millennium Park. But the image of David is fake. The Millennium Park website explains:

The fountain consists of two 50-foot glass block towers at each end of a shallow reflecting pool. The towers project video images from a broad social spectrum of Chicago citizens, a reference to the traditional use of gargoyles in fountains, where faces of mythological beings were sculpted with open mouths to allow water, a symbol of life, to flow out. Plensa adapted this practice by having faces of Chicago citizens projected on LED screens and having water flow through a water outlet in the screen to give the illusion of water spouting from their mouths. The collection of faces, Plensa's tribute to Chicagoans, was taken from a cross-section of 1,000 residents.

In other words, it would be possible to project an image of Michelangelo's David onto the tower, but it doesn't sound as if this has ever been done.

Update: This image comes from a Fark photoshop contest. It was created by a Farker named gigglechick.