The Minbar

stepping down the stairs
through a riot of pattern
such a young imam

The minbar is a pulpit in the form of a staircase on which the prayer leader stands when delivering a sermon after Friday prayer. The pulpit is usually situated to the right of the mihrab and is often made of elaborate carved wood or stone.

If you are interested in the Rameses slide, please go back and look at the additional info i have discovered today...i think this will be updated further.
It's entirely possible that more of these slides were of images taken by Felix Bonfils and only discovered in 1971.