A cave castle () or grotto castle (German: Grottenburg) is a residential or refuge castle that has been built into a natural cave. It falls within the category of hill castles. Unlike other types of castle (such as water castles), a cave castle can only be assaulted from the front. The castle gateway is usually located in the middle of a rock face, which makes it much more difficult to penetrate. Archaeological discoveries have revealed that caves were used as places of refuge as early as the Stone Age. The first medieval cave castles emerged in the 11th and 12th centuries. In the 14th and 15th centuries this type of castle became more widespread, especially in certain parts of France and Switzerland.