Some of the Best of Arizona
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As I have pointed out here before, there is so much more to northern Arizona than the Grand Canyon that I am glad you will be taking the time to show your parents around. And while there is some overlap, here's another list of similar resources. I don't know that you need a tour company for the Grand Canyon, there is a highway along the south rim with many turn offs to view the Canyon from different perspectives. There is also a good trail west from the main visitor center that you can walk for as long (or short) as you like. The visitor center offers all the information you could want on the Canyon and you can tour it at your own pace and without a guide. If you want to do an overflight of the Canyon, those are available from the small airport just south of the National Park in Tusayan.
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