First and foremost Castles are built so they protect their inhabitants from harm. A lot of thinking and planning went into the design to make sure the castle is unbreachable.
Here are 5 interesting facts and lesser known secrets of medieval castles:
5. The Moat
Everybody thought that the moat (the water that surrounds the castle) is only an obstacle that has to be overcome in order to get inside. In fact the primary function of a moat was to prevent the enemy from digging underground tunnels and storming in.