Actually Glenwood Springs is more like 2.5 -3 hours west depending upon where in Denver you are.
I love the Hotel Teatro right next to the 16th street mall. Fantastic mexican restaurant within walking distance as well as Larimer Square....It is pricey, but oh so worth it.
The art museum is really fantastic.
Boulder is fun, and you could stay there as it it is not too far from Denver and day trip over to Denver.