An image from Wikipedia—
"Verging on invisibility or immateriality, these works can provoke, mystify, or even go unnoticed. The very difficulty of seeing them demands an extraordinary patience in viewing them. Some emphasize the basic properties of their medium, be it photography, drawing, or sculpture, while others make it difficult to tell just what the medium is. Still others play with the distinction between language and image. And yet, in a world inundated with visual information, these works all revive the act of close looking as a source of meaning."
— National Gallery of Art, description of a current exhibition titled "There is nothing to see here."
See also Leslie Nielsen's rendition of this phrase.