That's Pasquino, the legendary venue for protest in Rome. He's just behind Piazzao Navona, in his very own Piazza Pasquina, though he's a modest little rascal and you'd have to have your eyes open to notice him (Cul de Sac, catty corner across the street, is a good wine bar, from which you can gaze in admiration).
In his day, Pasquino was the pride of Rome's "talking statues." "Talking," in the sense that Roman's liked to decorate him with scabrous verses and assorted political chitchat. Some samples are in the lower right-hand corner above. My old 1985 Blue Guide explains:
[A]s Stendhal noted on his visit to the city in 1816 'what the people of Rome desire above all else is a chance to show their strong contempt for the powers that control their destiny, and to laugh at their expense...'.They still do decorate him, apparently. As of last Thursday night, he bore the manifesto pictured at upper right above. You may not be able to read it, but trust me, it says "Siamo Il 99 %," "We are the 99 percent."
It was gone by next morning. Can't imagine why.