Arlington National Cemetery is the final resting place of many who gave their lives in service to the country. Two US presidents-John F. Kennedy and William Howard Taft-are buried here. The crew of the Challenger space shuttle, civil rights leader Medgar Evers and film star Audie Murphy are among the many honored here. The Tomb of the Unknown Soldiers, containing remains of unidentified soldiers from World Wars I, II, and the Korean Conflict, is guarded 24 hours a day. The changing of the guard ceremony is a moving tribute to them. Arlington House, the home of Robert E. Lee until the outbreak of the Civil War, is located on the cemetery grounds. Visitors may walk through the cemetery or board a Tour mobile Sightseeing tram.