1700 years to build. 5500 miles long. What were they trying to keep out?

European mercenaries searching for black powder become embroiled in the defense of the Great Wall of China against a horde of monstrous creatures.
The Great Wall keeps every mind human — it fights its subject at zero distance. The story fights on E8/E12 of the E0–E14 reality ladder, compressing militarism, culture, monsters, technology.
Films fighting at the same level of reality, about the same things.
Spaceballs (1987)E8/E12 · rare rung · militarism, technology
Batman Ninja (2018)E8/E12 · rare rung · culture, technology
(T)Raumschiff Surprise - Periode 1 (2004)E8/E12 · rare rung · militarism, technology
Redline (2009)E8/E12 · rare rung · culture, technology
Godzilla vs. Biollante (1989)E8/E12 · rare rung · militarism, technology
Team America: World Police (2004)E12 · rare rung · culture, militarismThe same preoccupations examined at another scale — one mind versus a nation.
Godzilla vs. SpaceGodzilla (1994)E6/E11/E14 · rare rung · militarism, technology
Pacific Rim (2013)E11/E14 · rare rung · militarism, technology
The Day the Earth Stood Still (2008)E9/E14 · rare rung · culture, technology
Godzilla 2000: Millennium (1999)E6/E13 · rare rung · militarism, technology
Godzilla vs. Destoroyah (1995)E6/E11 · rare rung · militarism, technology
Them! (1954)E14 · rare rung · militarism, technologyOther films that change a standing rule of their world — ranked first by those bending it at the same rung.
Nausicaä of the Valley of the Wind (1984)alters at E7 · same rung · rigorous
Mortal Engines (2018)alters at E7 · same rung · loose
Monsters (2010)alters at E7 · same rung · loose
The Silence (2019)alters at E7 · same rung · loose
Azrael (2024)alters at E7 · same rung · loose
Elevation (2024)alters at E7 · same rung · rigorous