The Zhonghua Gate (Chinese Gate) is a massive gate on the southern side of the Nanjing City, China which could hold 3,000 soldiers. It is famous because of its unique structure. Apparently, it looks like the regular imperial-style gate with its two sets of ornamented doors made from thick and sturdy wood. But the unique part is that there is a third set of stone doors that are not visible from outside the city gates. In ancient times, if enemies managed to push through the wooden doors and enter the city, the stone doors would fall into place and trap them in the courtyard till they were killed.