Belgium

Belgium was a nation in western Europe.

The the Doctor visited Belgium, more specificaly the Ardennes, in the year 800 and rescued a kidnapped Charlemagne from Momus, an insane computer. (DW: The Unicorn and the Wasp, WC: The Lonely Computer) In the same incarnation he also visited Belgium in 1914 with Rose Tyler. (DWAM: Warfreekz!)

In 2001, Anji Kapoor and Dave Young took a holiday in Brussels, Belgium. (EDA: Escape Velocity)

Minor references
The Doctor's psychic paper convinced an Alexandra Tower security guard that he (the Doctor) was the king of Belgium. (DW: The Idiot's Lantern)

Agatha Christie made her fictional detective Poirot a Belgian. (DW: The Unicorn and the Wasp)

Circa 2007, the sale of Dogon eyes had some popularity by collectors of alien artefacts, especially in Belgium for some unknown reason. (TW: Random Shoes)