Pentagon City is an unincorporated neighborhood located in the southeast portion of Arlington County, Virginia. It is located near The Pentagon and Arlington National Cemetery. Pentagon City is located less than a mile from the Potomac River, which separates the Commonwealth of Virginia from Washington, D.C. It is located on the Blue and Yellow Lines of t…Pentagon City is an unincorporated neighborhood located in the southeast portion of Arlington County, Virginia. It is located near The Pentagon and Arlington National Cemetery. Pentagon City is located less than a mile from the Potomac River, which separates the Commonwealth of Virginia from Washington, D.C. It is located on the Blue and Yellow Lines of the Washington Metro, and the Pentagon City Metro station is one of the busiest in the Metrorail system during peak and off-peak hours. It's located two miles away from the National Mall in downtown Washington. The area is a popular site for hotels and businesses.