I was very impressed with the urban environment of Grand Canyon Village, within Grand Canyon National Park. The Rustic and Neo-Prehistoric architecture was great to look at, fit in with the ponderosa forest, and provided a quaint "home base". It was so noteworthy that I
took pictures of the little community, and probably covered it more extensively than anyone besides the National Park Service itself.
On the other hand, I saw very little in Tusayan, the gateway community, that was worth seeing from an urban or architectural standpoint. There were a couple hotels that may have been 60-70 years old, but that was it. I think there's some historic airport buildings, as well. It has not seemed to be worth my time going around.
I am visiting Estes Park, Colorado, in a couple weeks. That seems to be maybe the best gateway town for all the National Parks in the US (but I could be wrong). Included in the historic architecture is the Stanley Hotel, of "The Shining" fame, and the Park Theatre, the oldest movie theater in the US. I'm planning on doing a little phototour (and then photothread) of Estes Park.