Iconic Photos (via Tabitha Hale of Rare) has the backstory for the photo:
In May 1988, President Ronald Reagan traveled to Moscow for his 4th summit with Mikhail Gorbachev. The Soviets prepared a grand welcome; buildings across from the Kremlin were repainted, streets repaved and trees and flowers planted along the boulevards.
The most telling incident was only revealed 20 years later. In the above photo, the man with the camera around his neck standing behind the boy was the current Russian Prime Minister (and former president) Vladimir Putin. He was pretending to be a tourist on his capacity as a KGB agent.
Russia denies the man with the camera is Putin.