You are on the first floor level looking south at a north facing wall.  The alcove to the front-right may have been an access to the south-west tower.  Note the plaster on the far wall.   The floor has been added digitally in this composite image to illustrate the levels.  Here the floor is show with full coverage but may have been partial with mezzanines. 

While you have a barrel vaulted stone ceiling there is another floor above.

You can turn around and look behind you or go through that opening forward left which will take you to staircases going up or down.