This. And The Wall.
The Great Wall was started before 200 B.C., but much of what we see today was rebuilt in the 1500s Ming dynasty, when Zheng He's epic around-the-world voyage occurred. His fleet was 300 ship strong, with the capital ship's size comparable to modern day aircraft carriers. Here is an image comparing Zheng He's ship and Columbus':
Sadly, after the voyage, they decided they didn't want anything to do with the rest of the barbarian world. The emperor declared it a capital offense for anyone to own a ship with more than one mask, and ordered to build/rebuild the wall.
Incidentally, Zheng He was a Muslim.