The Kimmel Center is Philadelphia's main performing arts complex and the home base for much of the city's classical music, jazz, dance, theatre, and touring performance calendar. Its glass-vaulted public space also makes it worth a look even if you are not holding a ticket.
Check the schedule before you go. On a good night this is one of the easiest ways to plug into Philadelphia's cultural life, with venues ranging from full orchestral scale to smaller, more intimate rooms.