Red Rocks is a Denver Classic! It is open during the day until 1:30pm, to check out the amphitheater and see the Red Rocks Museum.
Boulder is a 45 minute drive, with gorgeous views of the Flatirons and fun shopping/restaurants on Pearl Street.
Golden has a cute little downtown with a nice walk along Clear Creek. You can see the famous Coors Brewery, there are also lots of great hikes around Golden. Hikes: Table Mesa Chimney Gulch (more difficult) Matthew Winters (closer to Red Rocks)
Wash Park is a great park for going on a walk and relaxing. Here you can see how active Denverites can be! Lots of people walking dogs, roller blading, biking, jogging, and enjoying Denver fall weather.
Beautiful Botanic Gardens right in the heart of Denver. The Botanic Gardens is one of our favorite places to go!
If you like amusement parks, Elitches is a Denver staple!