This chamber, a full 30 feet below the Upper Dungeon, isn't made of stone blocks, it's hewn from the living rock of the earth.  10 by 15 feet, its domed ceiling and walls show the tool marks its excavation.  There are numerous lines of filth on the walls marking the various levels that water has risen up the walls during previous rainy seasons.
The Lower Dungeon Guard Room, Dungeon
king
visitor
I come to see the king when in town. I do not like the peasants of the castle. I am good friends with the king,
Sire! Do you not recognize your old friend? Has it been so long that a simple beard and change of robes has made your friend, Arthur, invisible? Arthur! I had no idea it was you! And you've lost quite a bit of weight too, I see. Is Margaret not baking her famous cakes for you anymore? Ah, you old bastard always a tease. The ol ball and chain has got me on a diet for my own good. Not that the smell of this chamber doesn't do a good job of ridding the appetite itself And why are you in this room? It's quite the mess and, as you said, smells horrid. Just look at the filth! As you can see there was quite an unsightly occurrence taking place in the not too distant past. I am simple putting away some of the mess Fair enough. I will speak no more of it. You must join the Queen and I this evening for dinner! But of course, sire. I would be honored!  Fantastic. I would advise, however, a long bath before coming. I wouldn't dream of entering a banquet hall of yours smelling like the peasantry that coats these walls Good! Because I'm serious about my dinner. I love a good roast, a good steak, some good stew and some fried onions. I am serious when it comes to fine dining! Margaret would kill me if I were to eat like we shall in my own home. The feast is on! Good! And please, send my best to Margaret, the dear.