Whereas the positive tourist travels to see what is there, the negative tourist travels to see what is not there. Travel he must, because the absences are only visible at specific sites. Tourist agencies promote the visibility of these spectacles with pointers, telescopes, and helicopter rides. Other parties try to render the absences invisible. For instance, after the theft of the Mona Lisa in 1911, crowds thronged to the Louvre to view its absence. Curators eventually filled the gap by shuffling the order of the ambient paintings. Efforts to erase the absence sometimes yield new ways to perceive the absence. Once the suppresser detects the backfire, he attempts another erasure. Since this may itself backfire (thanks to the machinations of the friends of the absence) an arms race develops. This tug of war helps us to articulate the conditions under which absences are visible—and invisible.