Shang-Tu

Shang-Tu, (TV: "Mighty Kublai Khan") also called Xanadu (PROSE: Iris Wildthyme y Señor Cientocinco contra Los Monstruos del Fiesta) was a Chinese city. Shang-Tu was the location of the Kublai Khan's summer palace in 13th century Cathay. (TV: "Mighty Kublai Khan")

History
In 1289, the First Doctor, Susan, and Barbara Wright visited the Khan in the city, having travelled all the way from the Plain of Pamir. A day later, they all set out for Peking, including the Khan himself. (TV: "Mighty Kublai Khan")

Iris Wildthyme, Tom, and Panda visited Xanadu and encountered Kubla Khan, who gave Iris a hookah. (PROSE: Iris Wildthyme y Señor Cientocinco contra Los Monstruos del Fiesta)

Behind the scenes
In the real world, Xanadu is another name for Shangdu, which was (in retrospect) archaically referred to as Shang-Tu in TV: Marco Polo.