It is a big hole. Lots of rock, a tiny, tiny river down at the bottom, pretty hot in the summer. At least that's how we joked about seeing the Grand Canyon on the way there; our oldest asked (first time funny, 167th time not as funny) “Are we just gonna look into a big hole for five days?”
The thing is once you see it, it becomes more than a big hole. On Day One we were sucked dry just by the colors and size of it all. We couldn't believe the way the Canyon changed in the sunrises and sunsets by Day Two.
After some Ranger programs on Days Three and Four we understood how it was formed and could imagine the desert as the ocean floor bottom, and identified fossils under our feet. By the time we hiked down into the Grand Canyon, we were captivated, awed, impressed and wouldn't have traded the week for a month of theme park passes.