Hong Kong

Hong Kong was a city on Earth.

History
The Brigadier met the Eighth Doctor in Hong Kong in 1988 where they encountered the Embodiment of Gris. (NA: The Dying Days)

Sarah Jane Smith assisted the Seventh Doctor in 1997 whilst investigating the Cortez Project in Hong Kong. (PDA: Bullet Time)

In 2048 China was taken over by Hong Kong. (NA: St Anthony's Fire)

Alternate timelines
In an alternate timeline, UNIT entered into Hong Kong in 1997 24 hours prior to the British handover of sovereignty to the Chinese to accquire the technology of a crashed Chinese stealth bomber. (BFDWU: Sympathy for the Devil)

Behind the scenes
Complete film telerecordings of all four episodes of The Tomb of the Cybermen were found in Hong Kong TV station RTV/ATV and returned to the BBC in late 1991.