Hundreds of thousands of people have braved freezing temperatures to see Barack Obama in Washington. A huge concert has been held to mark Tuesday's presidential inauguration, featuring such stars as U2, Bruce Springsteen and Beyoncé. The event reflected the popular excitement about his choice as the first black US president. Accompanied by his wife, Michelle, and their daughters Malia and Sasha, Mr Obama nodded along to the music at the concert, which included Stevie Wonder singing Higher Ground and U2 paying tribute to Dr Martin Luther King Jr with Pride (In the Name of Love). Mr Obama sang along as folk singer Pete Seeger led the crowd in Woody Guthrie's patriotic anthem This Land is Your Land. Between the songs, actors Denzel Washington, Laura Linney and Tom Hanks gave speeches that evoked past crises in US history, including the Civil War, the Depression and the Cold War. As Mr Obama prepared to be sworn in he stressed the depth of the challenges that he faces, including the recession and the unfinished wars in Iraq and Afghanistan, but said he was optimistic about the country's ability to face them. "There is no doubt that our road will be long, that our climb will be steep. But never forget that the true character of our nation is revealed not during times of comfort and ease, but by the right we do when the moment is hard," he said. "Despite the enormity of the task that lies ahead, I stand here today as hopeful as ever that the United States of America will endure, that it will prevail, that the dream of our founders will live on."