U.S. President Barack Obama hopped across the Potomac River to pay tribute to America's fallen soldiers at Arlington National Cemetery in Virginia on Monday.  Stating that his role as commander in chief is his most solemn responsibility, Obama placed a wreath at the Tomb of the Unknowns in honor of the 2011 Memorial Day.  Arlington Mansion and the 200 acres of ground immediately surrounding it were officially designated as a military cemetery on June 15, 1864, by Secretary of War Edwin M. Stanton.  Today, more than 300,000 people are buried on the grounds with funerals, including interments and inurnments, averaging 28 a day.  Among the notable Americans buried here are Presidents William Howard Taft and John F. Kennedy, Jacqueline Kennedy Onassis, and Robert Kennedy.  Located just across the Potomac River from Washington D.C., more than 4 million people visit the cemetery annually. 

Here's a look at this solemn place and its aweing symmetry: