Calais was a town in France.
The Spanish Armada was launched from Calais and later defeated by England. (AUDIO: The Flames of Cadiz, The Devil's Armada)
On 3 September 1939, Romana II rode the Transcontinental Express from Calais to Vienna. (AUDIO: A Blind Eye)
In 2016, a camp for refugees trying to get to England was set up in Calais. Amira and Yana stayed in this camp during their journey from Syria to London. (PROSE: The Stone House)
Rose Tyler suggest that to visit the Moon would be like visting Calais for the Doctor. The Tenth Doctor acknowledged that the Moon was Calais to the Earth's Dover. (PROSE: I Am a Dalek)