The event is Fatty's 100 Miles Of Nowhere. If you are not familiar with this concept, in a nutshell we are to ride either stationary trainers or around a very small course for 100 miles in support of charity. Fatty explains it so much better here.
The race is going to benefit a very deserving cause this year - Camp Kesem. To quote from their webiste:
"Camp Kesem empowers college student leaders nationwide to create free, life-changing summer camps for children affected by a parent’s cancer."