Run the Roc, Tri the Roc, and Du the Roc. The Flower City Challenge includes a half marathon, 5K, duathlon as well as a triathlon.The Half marathon is a sanctioned and certified USATF event. The triathlon includes a 5K run, 20 mile bike ride and 3-4 mile paddle. The duathlon consists of a 5K run, 20 mile bike and a 5K run. Register to participate or just come cheer on the athletes.