There are tons of amazing hikes in Rocky Mountain National Park. Longs Peak 14,000 ft. Mountain if you're really feeling adventurous and in very good shape. You'll need to start early - 5am. It's a challenging hike. but you do not need climbing gear.
A scenic drive through Glen Haven. If you're planning to come up Hwy 34, take the scenic route through Glen Haven. It's beautiful. Glen Haven is the smallest possible town, so there's nothing really to do there, but the drive is very nice.