Out of the four choices, I chose the Stairwell Challenge. I love the concept of spending the next eight weeks virtually climbing floors in different buildings in eight different cities. The flights naturally increase each week of the challenge. The challenge also focuses on constant hydration (bonus points!). UCR is using 15 steps to equal one flight of stairs, and promoting the recommended 64 oz of water per day.
The first building is the Old Post Office (18 flights) in Washington, D.C. It's an absolutely gorgeous building too!