Windsor Castle. Windsor Castle is a royal residence at Windsor in the English county of Berkshire. The art collection at Windsor Castle is part of the Royal Collection, one of the largest and most significant in the world. It includes notable works such as Anthony van Dyck’s portraits The Five Eldest Children of Charles I and Charles I in Three Positions, Rembrandt’s The Shipbuilder and his Wife, and Peter Paul Rubens’ The Adoration of the Magi. The collection also features portraits by Sir Thomas Lawrence and Hans Holbein the Younger. These artworks are displayed in the State Apartments and Semi-State Rooms, which are open to the public most of the year, with access depending on official events. The original castle was built in the 11th century after the Norman invasion of England by William the Conqueror. Since the time of Henry I, it has been used by the reigning monarch and is the longest-occupied palace in Europe. The castle's lavish early 19th-century State Apartments were described by the art historian Hugh Roberts as a superb and unrivalled sequence of rooms widely regarded as the finest and most complete expression of later Georgian taste. Inside the castle walls is the 15th-century St George's Chapel, considered by the historian John Martin Robinson to be one of the supreme achievements of English Perpendicular Gothic design. Originally designed to protect Norman dominance around the outskirts of London and oversee a strategically important part of the River Thames, Windsor Castle was built as a motte-and-bailey, with three wards surrounding a central mound. Gradually replaced with stone fortifications, the castle withstood a prolonged siege during the First Barons' War at the start of the 13th century. Henry III built a luxurious royal palace within the castle during the middle of the century, and Edward III went further, rebuilding the palace to make an even grander set of buildings in what would becomethe most expensive secular building project of the entire Middle Ages in England. Edward's core design lasted through the Tudor period, during which Henry VIII and Elizabeth I made increasing use of the castle as a royal court and centre for diplomatic entertainment. Windsor Castle survived the tumultuous period of the English Civil War, when it was used as a military headquarters by Parliamentary forces and a prison for Charles I. At the Restoration of the monarchy in 1660, Charles II rebuilt much of Windsor Castle with the help of the architect Hugh May, creating a set of extravagant Baroque interiors that are still admired. After a period of neglect during the 18th century, George III and George IV renovated and rebuilt Charles II's palace at colossal expense, producing the current design of the State Apartments, full of Rococo, Gothic and Baroque furnishings. Queen Victoria made a few minor changes to the castle, which became the centre for royal entertainment for much of her reign. Windsor Castle was used as a refuge by the royal family during the Luftwaffe bombing campaigns of the Second World War and survived a fire in 1992.