Montezuma Well is a sinkhole that filled with water and is now sort of a desert oasis.
I've never been to Flagstaff so I had expected it to be similar to Phoenix... basically in the middle of a desert. It actually looks more like the Pacific Northwest- complete with a massive looming mountain (Humphreys Peak), part of the San Fransisco Peaks- what are they doing in Arizona!?!. It was snow capped and even though we were already at around 7000 foot elevation, the top still looked way up there.
After passing through Flagstaff and switching to SR64, we got an even better view of Humphreys Peak and learned the top is at 12633 feet.