I loved Fort Collins
Are you a skier? If you enjoy the winter out of doors, snow shoeing, skiing, cross country skiing, go to Crested butte for a 3-4 day get away, Breckenridge, Vail, Steamboat springs-
Denver traffic is terrible be aware
Rocky mtn national park for snow hike, cross country skiing, etc
Hot springs in Mt Princeton, Glenwood springs, Salida
Estes Park is fun. If you like Stephen King, the Stanley Hotel is the inspiration for his novel 'The Shining'. Estes is also the gateway to Rocky Mountain National Park, a beautiful area for hiking and enjoying views. Lyons, Colorado is an artsy little town a bit of a drive from Boulder that has unique shops, art galleries and restaurants. If you have not seen a live show or done yoga at Red Rocks Amphitheater, that is a must do. For winter wonder, Steamboat Springs is a great town with a moderate to easy ski mountain, charming town, and hot springs to enjoy on a cold winter day! Golden is also amazingly cute with a scenic walkway along Clear Creek that is irresistible when the weather is gorgeous the creek sparkles. I could go on and on...