Skyrise is an annual event that benefits the Rehabilitation Institute of Chicago. It's the run (or more typically 'the walk') to the top of the Willis Tower. RIC is a great organization that helps so many people, and many of the patients show up at the event to participate or even hand out the medals.
It may sound like one of those physical challenges that is above your activity level. But believe me, it's not. It may be difficult, but you can do it at your own pace and there are many places to take a break along the way. And when you see some of the inspirational people involved, you'll be really glad you decided to do it. There are people that participate that could barely walk a few years ago. There are soldiers back from serving overseas. There were a few local celebrities like Bulls guard Ronnie Brewer. And there are a number of firemen that walk up all 103 floors while wearing all of their tactical gear.
But the majority of people climbing those stairs are average, normal everyday folks like you and me that just want to help out.