大興安嶺山脈
Although the Russians were thus deprived of the right to navigate the Amur River, the territorial claim over the lower courses of the river was not settled in the Treaty of Nerchinsk of 1689. The area between Uda River and Greater Khingan mountain range (i.e. most of Lower Amuria) was left undemarcated and the Sino-Russian border was allowed to fluctuate.