City Wall of Nanjing

Around 7 million cubic meters (250×10^6 cu ft) of earth were shifted to create one of the largest city walls ever constructed in China.

However, it was decided to bring Lion Hill to the northwest into the city defenses for strategic reasons, and this almost doubled the area the walls would encompass.

Originally, thirteen gates were built through Nanjing’s walls, but this number had grown to eighteen by the end of the Qing dynasty.

Different from ancient city walls in Beijing and Xi'an, its design and construction was unique and changed the old ways of equilibrium and symmetry.

Construction of the Beijing and the Xi'an city walls was in the ancient style of square or rectangular design.

When it was built by the second son of Emperor Zhu Yuanzhang, the 12-kilometer-long Xi'an city wall became the seat of local government.

All the brickwork joints were poured with mixed lime, water in which glutinous rice had been cooked, and tung oil because the coagulated mixture was very strong.

On top of the outer wall were 13,616 crenellations, or battlements, for defenders of the city to observe the enemy or dodge arrows.