Windsor Castle is a royal residence at Windsor in the English county of Berkshire. It is notable for its long association with the English and later British royal family and for its architecture.  

The original castle was built in the 11th century by William the Conqueror and was originally designed to protect Norman dominance around the outskirts of London and oversee a strategically important part of the River Thames.  

It has survived a prolonged siege during the First Barons' War at the start of the 13th century, the English Civil War, World War 2, and a fire in 1992.  Since the time of Henry I, it has been used by the reigning monarch and is the longest-occupied palace in Europe. Inside the castle walls is the 15th-century St George's Chapel, described as one of the supreme achievements of English Perpendicular Gothic design.   

It is a popular tourist attraction, a venue for hosting state visits, and the preferred weekend home of Queen Elizabeth II.