Caerlaverock Castle is a moated triangular castle first built in the 13th century. It is located on the southern coast of Scotland, eleven kilometres south of Dumfries, on the edge of the Caerlaverock National Nature Reserve. Caerlaverock was a stronghold of the Maxwell family from the 13th century until the 17th century, when the castle was abandoned. It was besieged by the English during the Wars of Scottish Independence, and underwent several partial demolitions and reconstructions over the 14th and 15th centuries. In the 17th century, the Maxwells were created Earls of Nithsdale, and built a new lodging within the walls, described as among "the most ambitious early classical domestic architecture in Scotland". In 1640 the castle was besieged for the last time by the Protestant Covenanter army and was subsequently abandoned. Although demolished and rebuilt several times, the castle retains the distinctive triangular plan first laid out in the 13th century. Caerlaverock Castle was built to control trade in early times.

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.