Around AD 1000 a wall was built around the hill against Viking raids. From 1100 the Redvers family built stone walls, towers and a keep over two centuries. Anthony Woodville, Lord Scales, obtained the castle in 1467 and added the Woodville Gate. Sir George Carey, Governor of the Isle of Wight from 1583, commissioned the Italian engineer Federigo Giambelli, who designed and built the fortifications from 1597. They were reportedly finished for 4,000 pounds.
The Elizabethan work is a squat rampart and ditch with bastions around the old castle and bailey. The well within the walls is 200 feet (61 m) deep, and 71 steps lead up to the keep. Princess Beatrice lived there from 1896 to 1944.
English Heritage manages it. The Great Hall and several rooms are open, and an upper room houses the Isle of Wight Museum.

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