Help with 360 Oblivion

[gaz@manc]

I'm currently in the Nenalata ruins. I've defeated all the skeletons and entered a chamber that has a set of stairs going down into a pit. When you place the crosshair over the stairs it says that the stairs are lowered automatically (or something like that). I can't figure out what to do or where to go next....surely the slog through the ruins can't be for nothing? The far wall in the pit has a rectangle stone coloured darker than the wall - is this a switch that can be activated somehow???????