赫連勃勃
Helian Bobo had intended that the city be absolutely impenetrable, so he commissioned his cruel general Chigan Ali (叱干阿利) as the architect and set extremely strict rules for construction. Chigan ordered that the soil used in constructing the wall be steamed, so that it would be hardened and difficult to attack, and he often tested the walls during its construction; if an iron wedge were able to insert even one inch deep into the wall, the workmen who were in charge of that section of wall would be executed.