The Keep

Carlisle castle.  Note the beginning of a long, shallow staircase on the right.  When gunpowder and cannons overtook swords and archers on the battlefield the keep was no longer provided suitable defense against attacking forces.  You didn't need to scale the enemy's walls if you could blow them down from afar.  

  The staircase was added to enable the movement of artillery to the roof of the keep. On the inside, a wall was built, bisecting the keep in order to provide reinforcement for the guns on the roof.  The result is a series of rather odd, narrow rooms.  Not the sort of place you would find comfortable for very long.