I found the patterns on the side of the Wells Fargo Center in Denver, Colorado, to be absolutely fascinating. The appearances of the building change rapidly throughout the day.
Old Fall River Road is a scenic and historic route from Horseshoe Park up to the Alpine Visitor Center. It follows one of the park's original roads, with plenty of hikes and waterfalls on the way up. This is one of the earlier streams just above the road's entrance.
The Butterfly Pavilion in Westminster, Colorado, has a fantastic selection of insects and even ocean creatures to view. The highlight of any trip to that location, however, is the butterfly house. If you ever visit, be sure to bring a macro lens with you! I've personally found that phone cameras work really well if you don't have any macro lenses!