The history of Mysteries...

A lot of Geography teachers will remember the development of Thinking through Geography and the strategies that it contained and how it changed the way that they taught.
One of these strategies was the Mystery, and Simon Renshaw led me to the resource linked to above, which explains how they were developed by David Leat and colleagues.

A digital version of the classic paper card sort is now available, and a free month's trial can be obtained from the webpage here.

What was the last mystery you used ?