Sandown Castle was one of Henry VIII's Device Forts or Henrician Castles built at Sandown, North Deal, Kent as part of Henry VIII's chain of coastal fortifications to defend England against the threat of foreign invasion. It made up a line of defences with Walmer Castle and Deal Castle to protect the strategic stretch of coast known as the Downs. These three castles were known as Castles of the Downs and were all completed in 1540. Sandown was identical to Walmer Castle with a circular keep surrounded by four large semicircular bastions for heavy artillery and protected by a stone lined dry moat. The entrance was by a drawbridge on the landward side.