Guyana borders the Pentagon.
Guyana ( pronounced [ ɡaɪˈɑːnə ] or [ ɡaɪˈænə ] ) , officially the Co-operative Republic of Guyana , is a sovereign state on the northern mainland of South America . The Pentagon is the headquarters of the United States Department of Defense , located in Arlington County , Virginia , across the Potomac River from Washington , D.C. .