score:6
In Arizona there is the Meteor Crater
There is the Continental Divide
There are Grand Canyon Caverns, but this may be a little out of the way but driving on old US-66 might just break the monotony and then get back on I-40.
There is the Mojave National Preserve.
Generally though you can probably find more on the Road Trip America site
Upvote:0
The Grand Canyon is wonderful, but a long way from I-40. Meteor Crater is close, and very underappreciated. It really is a cool spot. You will learn, relax, and have time to hike around a little. Which are all things that are good when on a long trip. I'm about to do a similar trip, from Winston Salem to Phoenix, along I-40 most of the way. In Arizona, Meteor Crater would be my #1 spot on that highway. :-)
Upvote:3
I would highly recommend the Painted Desert and Petrified Forest. They are near Holbrook, Arizona. Very interesting and great for taking pictures. You could get out of the car and stop and stretch your legs at several places along the drive through the parks.