Grand medieval castles were designed to be inaccessible to outsiders. Examples of these structures can still be found in many parts of Europe, often on small hills or other elevated landscape features. This elevation allowed those within the castle a clear view of the surrounding countryside, while making it more difficult to attack the castle. From the outside, a ditch filled with water often surrounded the castle and was known as a moat. A wooden fence called a stockade was sometimes built around the outside of the moat as a first line of defence for the castle. The drawbridge is the only passage across the moat into the castle and is controlled from within the castle. An iron grating called a portcullis is set into the doorway on the castle side of the drawbridge. The only other way into a castle is through a postern or postern gate, which is a small door that provides secret access to the main castle compound. The ramparts are heavy walls that enclose the main compound of the castle, called the bailey. Parapets are walls into which towers are set. The bailey is a large open courtyard which contained wooden structures such as living quarters, stables, and a chapel. Ramparts are either free-standing or built against earth embankments and are topped by stone battlements designed to screen defenders standing on the walls. Both ramparts and parapets can be topped with notched crenelations, which allow the defenders to repel attacks while being protected from harm.