A bowl-shaped depression, eh?
Mist can often form in such depressions, and can form quite monklike shapes, or shadows on the mist can. But because it's so dependent on particular conditions it can be difficult to repeat.

I once saw a monk standing by the edge of the road that disappeared when I got near to it. Shocked the hell out of me. Then, I saw another one that did the same thing. Then another. After the fifth one I thought this was less spooky and more interesting so I stopped. Turned out that the combination of my headlights, a light mist and some roadside posts was enough to create the illusion. Never seen it before - never seen it since.
(richardm, Mon 7 Jul 2008, 15:49, Reply)