You're looking at the Grand Canyon completely flooded by clouds, "a once in a lifetime event," according to park ranger Erin Whittaker. It didn't only happen once, she says, but two times in only three days:

The canyon gave us a second rare inversion in three days. Freezing fog dominated yesterday ... by the end of the day the sun was able to burn it all away no doubt making many first time visitors very happy. Word spread like wildfire and most ran to the rim to photograph it. What a fantastic treat for all!

This image of the event was taken by reader Tyner1000:

In reality, the event happens about once every decade but not with this intensity, she said. The fact that it happened twice is extremely rare. The phenomenon is called inversion: warm air on the upper parts of the cannon trap cold air and fog on the lower parts.

Here are some spectacular images from their Facebook page.