Sumatra

Sumatra was an island on Earth. (TV: "Assassin at Peking")

History
The island was part of Kublai Khan's empire. In 1289, the Khan tried offering the island to the First Doctor, should he win their game of backgammon, but the Doctor refused, insistent that his prize for winning should be his TARDIS. (TV: "Assassin at Peking")

On the same day as the volcanic eruption of Krakatoa in 1883, a sketch of the Ninth Doctor washed up on a beach on Sumatra. It eventually found its way into Clive Finch's collection of artefacts related to the Doctor. (TV: Rose)

In the late 19th century, Silas Beckett told Vastra and Jenny Flint that he was saved from an attack in Millwall by a Sumatran man. Jenny doubted this. (AUDIO: The Cars That Ate London!)

The Second Doctor, Jamie McCrimmon and Victoria Waterfield visited a post-21st century Sumatra. (AUDIO: The Great Space Elevator)