Sardicktown

Sardicktown was a city on a planet run by the Sardick family in the 44th century. At night, fog was prevalent throughout the town and sky fish swam freely. Since this included a shark-like species, Elliot Sardick created a machine that could control the clouds and fog to keep the fish away when people were on the streets. The Sardicks used permanent fog banks inside special chambers to keep people cryogenically frozen. (TV: A Christmas Carol)

Behind the scenes

 * The architecture of this town bears a strong resemblance to that of Victorian Britain. Why this occurs from the perspective of the Doctor Who Universe is unknown. However, from a real-world perspective, it is because the storyline of A Christmas Carol is based on the Charles Dickens novella of the same name.
 * Michael Pickwoad suggested Sardicktown was made from the colonists' ships, hence the metallic buildings. (CON: Christmas Special 2010)