The chinese city of was a british colonial territory that was returned to chinese control in 1997.

The transfer of sovereignty over Hong Kong from the United Kingdom to China referred to as "the Handover" internationally or "the Return" in China, took place on 1 July 1997, and marked the end of British rule in Hong Kong. Hong Kong's territory was acquired from three separate treaties: Treaty of Nanking in 1842. So the answer is Hong Kong