A moat is a deep, broad ditch, either dry or filled with water, that is dug and surrounds a castle, fortification, building, or town, historically to provide it with a preliminary line of defence. In some places moats evolved into more extensive water defences, including natural or artificial lakes, dams and sluices. In older fortifications, such as hillforts, they are usually referred to simply as ditches, although the function is similar. In later periods, moats or water defences may be largely ornamental. They could also act as a sewer.
The moat surrounding Matsumoto Castle
North view of the fortress of Buhen in Ancient Egypt.
A medieval moat castle in Steinfurt, Germany
The 17th-century fortified town of Naarden, Netherlands, showing bastions projecting into the wet moat
A castle is a type of fortified structure built during the Middle Ages predominantly by the nobility or royalty and by military orders. Scholars usually consider a castle to be the private fortified residence of a lord or noble. This is distinct from a mansion, palace and villa, whose main purpose was exclusively for pleasance and are not primarily fortresses but may be fortified. Use of the term has varied over time and, sometimes, has also been applied to structures such as hill forts and 19th- and 20th-century homes built to resemble castles. Over the Middle Ages, when genuine 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.
Dating back to the early 12th century, the Alcázar of Segovia, Spain, is one of the most distinctive castles in Europe.
Built in 1385, Bodiam Castle in East Sussex, England, is surrounded by a water-filled moat
The Norman White Tower, the keep of the Tower of London, exemplifies all uses of a castle including city defence, a residence, and a place of refuge in times of crisis.
Windsor Castle in England was founded as a fortification during the Norman Conquest and was one of the principal official residences of Queen Elizabeth II during her reign.