Windsor Castle is the largest inhabited castle in the world, and the oldest in continuous occupation (over 900 years). It is one of the Queen's three official residences, and is often said to be her favourite. The Royal Standard flies over the Round Tower of Windsor Castle when the Queen is in residence - at other times, the Union Jack flag flies in its place.Samuel Pepys proclaimed the Castle to be "the most romantique castle that is in the world". That was in 1666, and the same is true today.The origins of Windsor were in the 7th century Saxon settlement of Windlesora, where the present day village of Old Windsor is located. The town of Windsor is correctly known as "New Windsor" - the word "new" being used in a strictly relative sense!Windsor Castle was first built by William the Conqueror, following his invasion of England in 1066. The original structure was built from timber with earth fortifications. The Castle held an obvious strategic position on a steep hill overlooking the River Thames, and was part of a ring of castles around London, with the Tower of London, one day's march away, at its heart. The Castle was later rebuilt in stone, and grew in importance over the years. Henry II constructed the Round Tower and the original stone outer wall. Following the English Civil War, the Castle's primary role became that of a royal palace. The Castle has remained largely unchanged since the early nineteenth century, apart from the restoration work following the fire.The Fire of Windsor Castle took place on 20 November 1992 - ironically the 45th wedding anniversary of the Queen and the Duke of Edinburgh. During work on some of the State Rooms in the castle, a fire broke out in the north-east part of the Castle and rapidly spread to engulf many rooms. Fortunately most treasures and works of art had been removed temporarily and so few items were lost, although over 100 rooms in the Castle were badly damaged or destroyed. The fire took 250 firefighters some 15 hours to extinguish. The Castle was renovated, the aim being to restore the damaged rooms to their former glory using authentic materials and craftsmanship, and was re-opened in 1997 after five years of work. The cost of the renovation was 37 million pounds.