Buckingham Palace serves as the official London residence and administrative headquarters of the monarch of the United Kingdom. Located in the City of Westminster, the palace is a focal point for national celebrations and mourning. Originally known as Buckingham House, the building at the core of today's palace was a large townhouse built for the Duke of Buckingham in 1703. It was acquired by King George III in 1761 as a private residence for Queen Charlotte and became known as The Queen's House. During the 19th century, it was enlarged by architects John Nash and Edward Blore, who constructed three wings around a central courtyard. Buckingham Palace became the principal royal residence in 1837, upon the accession of Queen Victoria. The palace has 775 rooms, including 19 State rooms, 52 royal and guest bedrooms, 188 staff bedrooms, 92 offices, and 78 bathrooms. The State Rooms, used for official and state entertaining, are open to the public each year for most of August and September and on some days in winter and spring. The palace's ballroom, built in 1854, is used for state banquets and investitures. The Changing of the Guard ceremony, a major tourist attraction, takes place in the palace forecourt and is a precise drill performed by the Queen's Guard. The palace is not the personal property of the monarch but is held in trust by the Crown Estates for future generations. The Garden at Buckingham Palace is the largest private garden in London, featuring a lake and a helicopter landing area. The palace has been the site of numerous historical events and continues to play a central role in the British monarchy's public life.