Glen Canyon is revealing itself. David Brower, the first executive director of the Sierra Club and a three-time Nobel Peace Prize nominee, once said flooding Glen Canyon would be “America’s most regretted environmental mistake.” But almost 60 years after the fact, the full extent of that “mistake” remains mysterious…. Now, long-term drought has brought water levels in Lake Powell to historic lows. As the shores recede, they unveil Glen Canyon’s lost wonders, allowing the consequences to resurface. Gregory Natural Bridge is one such wonder.