Okay, it's technically not in Philly, but it's close enough, especially if making the trek across the Delaware River brings you to a 25,000-seat outdoor amphitheater in the summer (a cozy 7,000 fit inside in the winter months). Hosting huge rock and pop acts, the Susquehanna Bank Center is one of Philly's staples for catching the latest and greatest. You can gets seats on the lawn and bring your own blanket for a great warm-weather activity. The views of the Philadelphia skyline and the sunset at times can be a real treat. If seeing a larger group in an outdoor setting near the city sounds good to you, this place is worth checking out.