The Summer Palace in Beijing is the largest imperial garden in the world. It is a veritable museum of classical Chinese garden architecture. The initial construction of the Summer Palace began in 1750, commissioned by Emperor Qinlong as a gift for his mother's birthday. The construction took 15 years to complete. The plundering of foreign troops in 1860 destroyed most of the buildings, but they were renovated in 1888 by Empress Dowager Cixi.The central Kunming Lake covering 2.2 square kilometers was entirely man made and the excavated soil was used to build Longevity Hill.