People have been interested in castle for centuries. Historians and archaeologists have searched old documents and dug into castles to find out more about them. Because of this, for some castles we know who owned them, when they were used, when bits were built, what people ate, and what kind of things happened at castles. But there are lots of places where we know very little, not even when they were built. This is because a lot of medieval documents do not survive.