The Yuen Long Plain , in the northwestern corner of the New Territories, is the largest alluvial plain in Hong Kong. With an area of , it was formed between the time of the Tang dynasty (618907) and Song dynasty (9601279). It covers Yuen Long Town, Tin Shui Wai, Lau Fau Shan, Ping Shan, Shap Pat Heung, Hung Shui Kui, San Tin, Lok Ma Chau, Pat Heung, Kam Tin, Nam Sang Wai, Mai Po, etc.