Q: What lies in the blackness to which the eye is irresistibly drawn?

A: The basement. This was taken (with a Blackberry) leaning over the emergency stairwell on the 23rd floor of my old office building in Abu Dhabi.

The idea of depth – and therefore mystery –  depends crucially on the sunlight shining in through the glass exterior from the right, producing the shadows on the stairs on that side and the highlights on the metalwork on the left.