Constructed as part of the vast defensive network of Daxing—the grand Sui Dynasty capital that later became Chang'an—these ancient city walls defied the destruction that flattened surrounding regions. While modern builders rely heavily on rigid concrete and mortar to bond structures together, ancient engineers took the opposite approach: dynamic flexibility. The core of Daxing's fortification employed advanced rammed-earth techniques combined with mortarless interlocking masonry.
When a powerful earthquake strikes, rigid structures crack and collapse under seismic stress because they fight against the earth's lateral forces. In contrast, Daxing's mortarless construction acts like a massive kinetic shock absorber. By allowing individual stones, soil layers, and interlocking elements to shift, rub, and slide slightly against one another, the friction dissipates the immense energy generated by tectonic waves.
This phenomenon, known in modern engineering as seismic isolation and energy dissipation, allows the wall to roll with the shaking rather than snapping under strain. Furthermore, the foundation was constructed using meticulously compressed layers of varying particle sizes, creating a natural dampening pad that filtered out high-frequency vibrations before they reached the upper structure. Century after century, massive quakes rocked the region, yet Daxing's mortarless fortress stood intact, proving that ancient flexibility often trumps modern rigidity.