Sturdy enough.

The entrance to the cell.  It's only about 2' wide by 4' deep.  The walls are polished aluminum on one side and concrete on the other.   The door is steel.  The space is "light tight".  Very dark.   

A few more toys

This photo is a bit darker than I'd like it to be.   And it's an old photo.   On the left side is the closet where we keep leathers, straitjackets, diving suits, wrestling gear and so on.   The bare wood you see is now a cage area.  It has not yet been lined in black rubber but it will be soon.  The bondage bed/flogging station stands just in front of it there.  It will be more obvious how that works when you see people attached to it.  To the right and at the bottom of the wall is the entrance to our most private place.  You can barely make out the opening in this picture and that's okay with me.