In this video, a group of tourists learn the kind of behavior-- silence and respect-- that is expected of them at Arlington Cemetery's Tomb of the Unknown Solider. The Tomb of the Unknown Solider is a monument dedicated to American military service members who have died without having their remains identified. The United States approved the structure following World War I in March of 1921 and it has been continually updated with the remains of unidentified soldiers in World War II, the Korean War, Pearl Harbor, and the Vietnam War. The tomb has been guarded since November of 1925 to prevent vandalism and the disrespect of visitors picnicking on the slabs. Today, the tomb is still guarded 24 hours a day, regardless of weather conditions.