I hate to burst the wolf bubble-  That feature is way to shallow to hold a wolf, and I suspect that even wooden walls would not have been enough. I grew up with a wolf/husky mix, and she could escape from ANYTHING by digging, chewing, climbing, etc. I spent half my youth running her down after she would dig out under our fence. At the vet where we boarded her during our vacations to Florida she would climb the eight foot chain link to get out of the dog run (after they tried wiring the latch shut because she was flipping it with her nose). They finally gave up trying to restrain her because: A, they couldn't and B, she was not actually trying to run away. She only wanted to come up to the office and visit. Unless there was something pretty lethal going on in that pit feature like spikes, of which there seems to be no evidence, she would have dug out the side of it in minutes, walls or no. 
 
I like the potato pit idea.
 
 
Marty Pickands
New York State Museum