Today you can find Philadelphia's compact 5-square-mile downtown (William Penn's original city) between the Delaware and the Schuylkill (pronounced skoo-kull) rivers. Thanks to Penn's grid system of streets—laid out in 1681—the downtown area is a breeze to navigate. The traditional heart of the city is Broad and Market streets (Penn's Center Square), where City Hall now stands. Market Street divides the city north and south; 130 South 15th Street, for example, is in the second block south of Market Street. North–south streets are numbered, starting with Front (1st) Street, at the Delaware River, and increasing to the west. Broad Street is the equivalent of 14th Street. The diagonal Benjamin Franklin Parkway breaks the rigid grid pattern by leading from City Hall out of Center City into Fairmount Park, which straddles the Schuylkill River and Wissahickon Creek for 10 miles.
Although Philadelphia is the fifth-largest city in the nation (about 1.5 million people live in the city, 6.4 million in the metropolitan area), it maintains a small-town feel. It's a cosmopolitan, exciting, but not overwhelming city, a town that's easy to explore on foot yet big enough to keep surprising even those most familiar with it.