We've had all kinds of 'Your ---- pictures'. I thought I'd start at the bottom. Let's see pictures of holes in the ground. Canyons, mountain tops looking down, falls, etc. If you ridden there and you looked down into it, let's see it. I'll start
Grand Canyon, near Point Sublime on the north rim.
Moonset over the south rim from Point Sublime
Rowena Hills, Columbia Gorge
Picketwire Canyon, Colorado

Dinosaur trackway

1890's cistern. Literally a hole in the ground
Ape Cave, Mt. St. Helens