Grand Canyon

We have arrived at the south rim of the canyon.  At this point the canyon is 18 miles wide. That's how far away the distant level plain is.  If it weren't for the fact that you're looking across the top of a hole the curvature of the earth wouldn't let you see that far.
The immense size of the canyon cannot be displayed by ANY media.  It's one of those places that you must see with your own eyes to truly appreciate.