Right outside of Denver is the Lariat Loop scenic byway with plenty to see. It's to the west of Denver in the foothills to the Rocky Mountains and makes a great day trip (or half a day) of driving and light hiking. Perfect for kids, too. And everything is free.
I found the Lariat Loop national scenic byway in my handy road trip book that's always in my car; you never know when you'll have time for a scenic drive.
I stopped at the Dinosaur Ridge visitor center where you can park. Then you walk up the road that is closed to traffic. Or you can pay for a ticket to ride the tour bus. You quickly climb up the side of the hill and get a nice view. There are sites marked along the route showing fossilized dinosaur tracks, plants, and geologic formations. What a great way to get some fresh air, exercise, and learn a little.
Next stop is the Red Rocks Amphitheater and park. You can park and walk around this outdoor theater. The red rock outcroppings are dramatic, and the steep seating makes for a good urban hike. And the views down into the valley are nice.
I had time for one last stop before the rain started so I drove up the winding road to the Buffalo Bill museum. Park for free then take the short walk to his gravesite. You also get a great view of downtown Denver.
The Lariat Loop scenic byway ends up in Golden, Colorado where you can stop for a drink or snack before taking the short drive back into Denver.