Foremost among Donald Trump’s anti-immigrant rhetoric is his controversial promise to build a “Great Wall of Trump” along the United States-Mexico border. The scale of Trump’s proposed wall, even if it runs the entire 3,201km border, would pale in comparison to the Great Wall of China, the total length of which was 21,196km, although only 8,852km remains.

Trump says his Mexico wall will be like the Great Wall of China. Here’s why that comparison is terrible

The Great Wall was not the result of a single enterprise to keep the northern “barbarians” out; it began as individual walls erected by the northern states during the Spring and Autumn (770-476BC) and Warring States (475-221BC) periods, when the nascent Chinese nation was a collection of independent states.

The Great Wall of Trump: expensive, unrealistic and useless, experts say

While the northern stretches of these walls were built as defences against the nomads further north, other sections were erected along the borders of states.

After the first emperor of the Qin dynasty established a centralised empire in 221BC, he began to dismantle the walls that separated the previously independent territories in his realm, but he kept the northern walls intact, reinforcing existing sections and plugging the gaps.

The Great Wall was repaired several times over the next two millennia, and what we see today dates from the fortifications made during the Ming dynasty (1368-1644).

As a line of defence against foreign invasion, the Great Wall failed on many occasions, but its symbolic and cultural significance still resonates.