Portcullis room above the gate(d)

You stand in a room crowded with instruments of siege warfare, designed purely for the defense of this castle. The dominant item in the room is the portcullis, which rises out of a rectangular slit in the floor to tower three spans or more above your head. It divides the room into two separate spaces, though one can squeeze past on either end. On the same side of the room as the stairs are a turnstile and a series of pulleys, connected to the portcullis with ropes. On the other side of the room four archer's slits in the wall let light in, and the floor is scored with a number of murder holes. A large cauldron sits below a smoke vent against a side wall, where two buckets hang from pegs.
The only obvious exit is down.
A massive portcullis