This section of Colorado highway follows the Arkansas River from Cañon City to Salida. Outside of a short stretch bypassing the spectacular Royal Gorge near Cañon City, most of the road is within the river's picturesque canyon.
A stop at the busy Royal Gorge Bridge theme park is a must. The main attraction is the 1000-foot high suspension bridge; you can choose to walk or drive across it. I'm not sure which leads to more vertigo! There are a number of other theme park attractions here, including an incline railway that takes you to the canyon's bottom. While the park is often busy, the crowds won't detract from the experience.
Update: a June 2013 wildfire destroyed much of the theme park. It is currently being rebuilt; consult the park's website for opening hours and construction progress.