The New Territories is one of the three main regions of Hong Kong, alongside Hong Kong Island and the Kowloon Peninsula. It makes up 86.2% of Hong Kong's territory, and contains around half of the population of Hong Kong. Historically, it is the region described in the Convention for the Extension of Hong Kong Territory. According to that treaty, the territories comprise the mainland area north of Boundary Street on the Kowloon Peninsula and south of the Sham Chun River (which is the border between Hong Kong and Mainland China), as well as over 200 outlying islands, including Lantau Island, Lamma Island, Cheung Chau, and Peng Chau in the territory of HK.