Arlington sits directly across the Potomac River from Washington, D.C., in the Northern Virginia region. It is the site for the famous Arlington National Cemetery, established as an American military cemetery during the Civil War. The cemetery sits on the grounds of Confederate Gen. Robert E. Lee's home, Arlington House, and veterans from all the nation's wars are buried in the cemetery, from the American Revolution through The War on Terrorism in Iraq. President John F. Kennedy's grave is there, too, marked with the Eternal Flame. Other monuments include The Tomb of the Unknowns and the Iwo Jima Memorial. Arlington also is home to The Pentagon, the HQ for the U.S. Department of Defense. Bikers can enjoy the 23-mile self-guided tour of Arlington with 12 stops to learn history along the way. A great place to hike and bike is the W & O.D. Railroad Trail that traverses the urban heartland and countryside of Northern Virginia.