The Great Wall was designated a UNESCO World Heritage Site in 1987. More than 10,000,000 people visit the Great Wall every year! Over time the effects of wind and the exposure to the elements has deteriorated the Wall. But also new sections have been discovered through the years.
The Great Wall is actually much longer than Halliburton knew; total length is about 5500 miles! The portion he visited may have been a shorter, 1900 mile long section. As large as the structure is, it still cannot be seen from the moon as Halliburton suggests.
The last Emperor of Manchu was Henry Puyi and his Empress, the Manchu Princess, was Wanrong.
Extra: Watch a short video of the history, and present-day standing, of the Great Wall (TED-Ed: 4:29)