FLAGSTAFF, Ariz. (AP) — Most of the millions who visit the Grand Canyon each year take in its sweeping views from along the edge, where they can follow paved trails, grab a bite to eat or ride shuttle buses to scenic overlooks. But increasingly, more physically demanding activities like rock climbing, canyoneering and extended hikes are luring visitors into the park's depths. Now, Grand Canyon officials are exploring ways to manage those who venture below the rim and into more rugged terrain, and protect the park's resources.