Philadelphia is a walkable city, and most of the attractions are within walking distance. However, visitors can also use public transportation via the SEPTA system which includes buses, trains, and trolleys. A one-day transit pass is available for $9, which includes unlimited rides on all modes of transportation.
If you have more time, consider visiting the Eastern State Penitentiary or the Franklin Institute. For those who have less time, prioritize Independence Hall, the Liberty Bell Center, and Reading Terminal Market. Don't forget to try Philly's famous cheesesteak and soft pretzels while you're there.