The building materials for the Wall in the Qin and Han dynasties were mainly rock, clay, earth and stone; even wood and pottery tiles were used.．Generally speaking, at that time the building materials were quarried nearby. They followed the principle of “taking local materials and using them in accordance with their qualities. “When the Wall was built in the mountain areas, stone blocks were quarried right on the mountain. On the plains, the Wall was built with rammed earth or clay. While in the deserts, the Wall was built reeds and willow branches netted together to hold the sand. The Great Wall near the Lop Nur Lake was built in this way and can still be found. In Northeast China, some sections of the Great Wall were built with piles of wood and timber.
The Great Wall was filled up with hardened rammed earth, stones and rocks, and was covered up with large pieces of rectangular bricks.
During the Ming Dynasty, the Great Wall was rebuilt in most places. It was largely replaced by big bricks and evenly sized stone blocks. Fortresses were constructed at the strategic points along the Great Wall.