PHILADELPHIA, USA - JUNE 11, 2013: People visit Schuylkill Banks river walk in Philadelphia. As of 2012 Philadelphia is the 5th most populous city in

PHILADELPHIA, USA - JUNE 11, 2013: People visit Schuylkill Banks river walk in Philadelphia. As of 2012 Philadelphia is the 5th most populous city in

Marek Slusarczyk / Alamy Stock Photo

Image ID: 2AH0KX7

PHILADELPHIA, USA - JUNE 11, 2013: People visit Schuylkill Banks river walk in Philadelphia. As of 2012 Philadelphia is the 5th most populous city in the US with 1,547,607 citizens.