Cottonwood Hollow Natural Area, Fort Collins, CO. A quick glance out the window when I got up this morning convinced me the sunrise was going to be a good one, so I hurried to get dressed and drove to Cottonwood Hollow Natural Area. It is located south of Riverbend Ponds Natural Area and west of and adjacent to Running Deer Natural Area. The Poudre River defines its western and southern border. I was right about the sunrise! Raptors were running regular patrols over the area this morning, and I scared up a great blue heron along the river and a small herd of whitetail deer. I encountered a lone runner out on this glorious morning.