The Great Wall (Movie, 2017)

Tagline: "It took 1700 years to build. and is 5500 miles long. What were they trying to keep out?" Well, historically the Great Wall was intended to keep out barbarian invaders from the north. 

Damon does a good job in this captivating science fiction based on the premise that the great wall of China was built to keep out monsters. The film is set during the Song Dynasty (960-1279) and gunpowder was developed in China during that era.  The CGI special effects are stunning.