Instructor Abby Nelson scales a 10,000-square-foot wall at Chelsea Piers Sports Center in New York City in this undated handout photo. British climber George Mallory famously said he wanted to climb Mount Everest because it was there. But there or not, experts agree that climbing is a great workout, so if you cannot get to a mountain, fitness centers are bringing a mountain to you. To match Reuters Life! FITNESS-ROCKCLIMBING.