Apple just gave Good Morning America a first look at its secretive fitness lab, where it's spent the past few years putting employees through a battery of tests. And no, they didn't even know they were helping the company get ready for the Apple Watch, which packs in a bevy of sensors for health tracking. "We hooked them up with all the masks and so forth, but we would put on an Apple Watch covered up," Apple SVP of operations Jeff Williams told ABC. Still, we can't imagine Apple's workers didn't know something was up. Aside from all the sensors, and the fact that it's in a nondescript office building, the lab doesn't look that much different from your average gym -- it's packed with treadmills, fitness bikes, and rowing machines. And, most intriguingly, there are climate chambers which allow Apple to replicate a variety of different places (it also tested the Watch all over the world).