Query: What type of trees are on Purple Mountain?
Context: Surrounded by the Yangtze River and mountains, Nanjing also enjoys beautiful natural scenery. Natural lakes such as Xuanwu Lake and Mochou Lake are located in the centre of the city and are easily accessible to the public, while hills like Purple Mountain are covered with evergreens and oaks and host various historical and cultural sites. Sun Quan relocated his capital to Nanjing after Liu Bei's suggestion as Liu Bei was impressed by Nanjing's impeccable geographic position when negotiating an alliance with Sun Quan.