Four hills of Kowloon

At the end of the 18th century, Hakka settled into the Cha Kwo Ling area, and quarrying became their main occupation.

By that time, the villages of Cha Kwo Ling, Ngau Tau Kok, Sai Tso Wan and Lei Yue Mun were collectively called Sze Shan (四山, "Four Hills").

[2] In the early 20th century there were said to be more than 10 quarries in the Ngau Tau Kok section of the "Four Hills" alone, each employing 10 to 20 people, all Hakka with origins in the East River area of northeastern Guangdong.

The four villages also formed the Sze Shan Kung So (四山公所, "Communal Hall of Four Hills"), managing the quarrying business.

[2] The Old Quarry Site Structures at Lei Yue Mun (Kowloon) have been listed as Grade III historic buildings.