President Barack Obama And First Lady Michelle Obama, Walk With Former President George W. Bush And Former First Lady Laura Bush

President Barack Obama and First Lady Michelle Obama, along with former President George W. Bush and former First Lady Laura Bush, walk along the North Memorial Pool of the National September 11 Memorial in New York, N.Y., on the tenth anniversary of the 9/11 attacks against the United States, Sunday, Sept. 11, 2011. (Official White House Photo by Pete Souza)