A number of stones from a small stone circle were moved from farmland in nearby Tisbury and placed in the grounds of the castle. A few of these stones can be found behind the current ticket office.
The two largest stones appear to be weathered and pitted limestone, and are similar in shape to the pairs of stones (male and female) of the West Kennett Avenue at Avebury.
Why did someone think it was important to move stones from a stone circle to the castle?
Did someone in the past know about the connection between the castle and stone circles?
Was the location of the castle determined by the position of an existing well or spring? A reliable source of water would have been an important consideration when determining the site of a castle whose main purpose was residential rather than defensive.
The dimensions of the castle suggest that certain measurements and combinations may have been important, or significant. It is felt that the heart of the design may have been a hexagonal foundation within a circle of 120 feet, reducing to 118 feet for the castle proper. The tower extension is approximately 80 feet wide and built into the hexagon, thereby shortening two of the sides to approximately 36' 8" (11.2m). If this is taken to be the hypotenuse of a 30 degree triangle, the side opposite would be 31' 9" (9.7m) which just happens to be the length of the tower extension. It may be a complete coincidence that the walls of the inner courtyard appear to be 60 feet - 36' 8" = 23' 4" (7.1m), producing a ratio of 11:7 (that is, semicircle to diameter).
Note: The present foot measure was first standardised in England in 1305 (Edward I).