Great Wall of China

The Great Wall of Cathay, (TV: Marco Polo) or the Great Wall of China, (PROSE: Childhood Living) lay along the course of the Yellow River. According to the First Doctor, it was twenty feet wide. (PROSE: Childhood Living)

Geography
The ancient cities of Su-Chow and Kan-Chow, as well as Lan-Chow and the town of Sinju, were located along or near the Great Wall. (TV: "The Wall of Lies")

History
In 1289, Marco Polo's caravan travelled along the Great Wall for many miles. (TV: "The Wall of Lies")

The Tenth Doctor and Donna Noble visited the site of the Great Wall of China during the Qin dynasty, as it was still being built. (COMIC: The Immortal Emperor)

Before 2005, the Ninth Doctor visited the Great Wall of China and was photographed doing so. Clive Finch later showed this image to Rose Tyler. (PROSE: Rose)

In China, Harry's grandfather was once arrested, with his boyfriend, for attempting to steal a section of the Great Wall. (TV: Knock Knock)