I turned a 2-hour layover in Denver into a three day adventure there and my first time exploring in the Mountain region of America. We went as far south as Manitou Springs, then as far north as Estes Park where we stayed at the Stanley Hotel.
Being from Hawaii, I'm used to seeing mountain ranges, but not on the scale where the mountains stretch for miles, as far as the eye can see. Wow.
I also did my first fourteener - Pikes Peak, at 14,115 ft. At the top, is a visitors center with a gift shop and a donut shop that supposedly makes the best donut in the world. Yes, they are pretty good and I recommend you eat them.
Another thing we don't get in Hawaii is more than one season, and leaves changing colors. On the way up to Estes Park on Peak to Peak Highway, the aspen trees were just starting to turn yellow. Quick fact (that I hope I heard right): Native Americans would take the white bark of the aspen tree and boil it to be used as a remedy for headaches and other things.
There were many moments in Colorado where I wished I could be there during winter when the snow was falling. Also, no, I did not smoke marijuana but I did go into several dispensaries and the workers were always very nice and helpful.