Lit only by scattered torches, The dungeon lies far underneath the castle.  Bandits and Thieves who find themselves there are met with cold stone walls and floors, with chains and bars restricting movement.  Guards patrol the corridors, keeping an eye out for any escape attempt or misdeed.  The only comforts afforded in the Dungeon are the piles of hay for sleeping.
Dungeon, Inside Castle
rat
thief
I steal from people to gain wealth. I don't care about others. I am angry and mean.
I'm innocent, just like everyone else here! Sure, I've heard that one before Truly. Look at these hands. Are these the hands of a theif? Do thieves have a particular look to their hands? That makes no sense Don't touch my things, Rat. I may be a common thief, or so I'm convicted, but at least I'm no garbage eater At least I have food Watch yourself, Rat. Or you may soon become the food. You aren't fast enough to catch me Settle down, Rat. If I can steal this chain I can put you in my own personal 'food chain' which is what I call this device. Just ask the last rat that was here. I'll be sure to eat you when they execute you Ha! Execute me? Surely you jest. The executioner is a friend of mine, he will fake the hanging and I'll be as free as you are! The executioner that had a heart attack last week? Oh, that's too bad for you then. 