From their event page: 

Proclaim Liberty of Movement throughout Center City Philly a day early at the (3rd Annual) BELL LAP!  We’ll ride around town at a stately pace, ringing our bicycle bells while passing the Independence Hall and several notable and historic bells. You should have a bike bell or horn on your handlebars (or be ready to say, “ding-ding” loudly, from time to time). This ride will end close to the start, at a congenial tavern. There will be some modest prizes and maybe a recitation. FREE, of course.