I'm a fan of the HBO show Game of Thrones.
The show is set in the medieval-looking kingdom of Westeros.
In the frozen north beyond Westeros, there are hordes of barbarians called "wildlings."
To keep invading hordes out, ancient Westori built a giant wall spanning the country.
The concept is pretty fanciful.
Except it's based on reality.
More than 2,000 years ago, a man named Qin Shi Huang conquered several neighboring nations in what's now known as Asia.
To protect his new empire from the aggressive Xiongnu in the north, Qin Shi Huang decided to connect several ancient fortresses into a single gigantic wall.
Sixteen centuries later, Qin Shi Huang's wall still stood, having been rebuilt and buttressed over the years.
But the country he'd unified, now under new rulers was under siege. Again and again, huge masses of nomad warriors on horseback were riding down from the north and sacking cities.
The rulers of the land decided to re-build the Wall. They built 25,000 watch towers along it. They stretched its length to 13,000 miles.
These wall-builders were the Emperors of the Ming dynasty. Their wall was what we now know of as the Great Wall of China.
Good morning! The sun was up outside my room at the Kerry Hotel in Beijing.
That meant it was time to head downstairs to meet my tour.
After a short wait, they arrived.
See the rest of the story at Business Insider