A castle is a type of fortified structure built during the Middle Ages predominantly by the nobility or royalty and by military orders. Scholars debate the scope of the word castle, but usually consider it to be the private fortified residence of a lord or noble. This is distinct from a palace, which is not fortified; from a fortress, which was not always a residence for royalty or nobility; and from a fortified settlement, which was a public defence – though there are many similarities among these types of construction. Usage of the term has varied over time and has been applied to structures as diverse as hill forts and country houses. Over the approximately 900 years that castles were built, they took on a great many forms with many different features, although some, such as curtain walls, arrowslits, and portcullises, were commonplace. - (from: https://en.wikipedia.org/wiki/Castle)
This is King Charles II of England who, in 1681, gave the State of Pennsylvania to William Penn.
Mini-introduction to Castles
What was it like to live in a castle?
Medieval methods are used to build a NEW castle in France.
Archaeologists dig at a ruined castle to learn it's history.
Archeologists explore a castle moat and find a gold coin from the 1300's.
Siege!
How Castles were built.
What did Castles look like inside and out? It isn't what you think!