Although the Liao built walls around 1138, their achievements were minimal compared to others like the Jin who built extensively beforehand. The bulk of the Liao building took place in 1181. Further construction was completed by 1198.
Both the Liao and the Jin introduced technical innovations into their wall building. Some of the Jin walls have an outer moat and wall, as well as an inner moat and a main wall. The inner moat ranges from 33-197 feet wide. Jin walls also had beacon towers as well as semicircular platforms on the outside called `mamian' or `horse faces,' in addition to battlements and [G 16 / parapets].
The Jin's longest walls are in Inner and Outer Mongolia. When the [G 12 / Mongols] swept across China, frontier walls were rendered useless. Not until the Mongol empire began to fall apart did wall building re-emerge in China.
