Arlington is a county which consists of 210,000 residents of the northern tip of the Commonwealth of Virginia. It is located just across the Potomac River from Washington D.C. It is incorporated as a central city of the Washington Metropolitan Area. It is the smallest self-governing county in the nation. Arlington was ranked 1st of many walkable cities by the American Podiatric Medical Association in 2005, and the most educated city by CNN Money in 2006. Since the county used to be a part of the nation's capital, there are many national landmarks and memorials here that can be found in the business directory. The Arlington National Cemetery, the Pentagon, Air Force Memorial and Reagan National Airport all call Arlington home. The Arlington National Cemetery was established during the American Civil War as an American military cemetery. Located on the grounds of General Robert E. Lee's estate, there are roughly 300,000 people buried here making it the 2nd largest national cemetery in the country. Veterans from every war the USA has been in are buried here. The Tomb of the Unknowns is also a major attraction at the cemetery; it stands for every soldier that has been lost, unrecognized or otherwise unknown.The Pentagon is also a major attraction in the county. It is the headquarters of the U.S. Department of Defense, and is the world's largest office building. The Pentagon has five floors and houses over 23,000 civilian and military employees year round. It has been targeted for attack numerous times since it's dedication. More information on this government building and others can be found in the yellowpages of Virginia.