Out of context, without the background, it would appear to be completely bizarre behavior. Gathered here in this plaza by the hundreds, everyone is doing strange things. One man holds his arms up and to the side, the palms of his hands flat, as if pushing back some strong, invisible force. A woman in a sparkling dress pretends to kick something down, a look of determination on her face. Still others squeeze their fingers together, seeming to dangle an unseen object. And everybody’s getting their photo taken, in the act. Behind them all—the Leaning Tower of Pisa. A marvel born out of mistake, today its image is unmistakable, one of those ubiquitous landmarks that’s instantly recognizable, from film and television to the wallpaper of every old-school pizza parlor you’ve ever visited. And while taking and posting a joke photo, pretending to hold it up, or push it down, or dangle …