Crystal City is an urban neighborhood in the southeastern corner of Arlington County, Virginia, south of Downtown Washington, D.C. Due to its extensive integration of office buildings and residential high-rise buildings using underground corridors, travel between stores, offices, and residences, it is possible to travel much of the neighborhood without going above ground, making at least part of Crystal City an underground city.

Arlington County, or simply Arlington, is a county in the U.S. state of Virginia. The county is located in Northern Virginia on the southwestern bank of the Potomac River directly across from Washington, D.C., the national capital.