this secret tunnel is like a vein to the castle.  It leads to many other rooms within the castle.  This includes passage to the dungeon, the throne room, the kings chambers, and a secret exit to the outside.  You must be careful because the tunnel is small to maintain its secrecy.  There are 5 different rooms to the castle that can be accessed through this room. This also proves as a good escape route as enemies with large armor will not be able to fit through.
Secret Tunnel, Inside Castle
king
rabbit
I live in a glade near the village.  I am afraid of the fox.  I run fast when the fox chases me.
*sniffle* Give me back my scepter! Now, I wonder if the enemies have been using this tunnel to escape? (eyes filled with a want to kill) You're a fearsome rabbit with wild fangs! Go away or I will have my guards kill you. *gives scepter back* There, there! Now that's the way a rabbit should behave! Look how this tunnel branches out. I could go almost anywhere in the castle! I can talk and I need to tell you about your future... An enchanted talking rabbit! Please, do tell me! Anguish, death and defiance... *disapears into the cavern* Goodness! If what you say is true, I need to have these tunnels dug up. I cannot allow my enemies to reach me. its fine Fine? Fine? You have predicted a horrible death for me! That is hardly fine!