A short, easy hiking trail in Morrison (across from Red Rocks) along a hogback that exposes some of the world's best-preserved dinosaur tracks — over 300 footprints from large herbivores and predators that walked on a Cretaceous beach roughly 100 million years ago. The visitor centre at the bottom explains what you're looking at; rangers lead free guided walks at weekends.
Easy to combine with Red Rocks Amphitheatre and Morrison itself (an old mining town now full of small restaurants and bike shops). Allow about two hours for the walk.