The garden at Buckingham Palace,the official London residence and working headquarters of the British monarch, is a 39-acre walled oasis in the middle of the city and its largest private garden. Called the Queen’s garden, it is where Queen Elizabeth II holds her summer garden parties. The central feature of the garden is a three-acre lake created in the 19th century. Other highlights include a 156-meter herbaceous border, the wisteria-clad summerhouse, the rose garden, and one of Britain’s biggest garden ornaments — a 15-foot Waterloo Vase carved from a single piece of marble weighing an estimated 20 tons. It also includes the palace tennis court, where King George VI played Wimbledon champion Fred Perry in the 1930s. Timing and a little bit of luck are needed to see this garden. It is only open for tours in April, May and June and then only when the queen is not in residence. Tours are limited to 25 visitors.