Philadelphia, located in southeastern Pennsylvania , in the mid-Atlantic region, is the fifth most-populous city in the United States. Often referred to as "Philly," the city is coterminous with Philadelphia County. Philadelphia sits adjacent to the New Jersey and Delaware borders, and as such, its metropolitan area encompasses counties in Pennsylvania, New Jersey and Delaware.
For most visitors, the landing point will be Center City, the "downtown" section of Philadelphia. It is bounded by Vine St. to the north, the Delaware River to the east, South St. to the south, and the Schuylkill River to the west. The 2010 Center City residential population of 57,000 makes it the third most populated central business district in America, behind New York City and Chicago . Other popular districts to visit are Old City, West Philly, and South Philly.