THE oldest part of the Great Wall of China, which was built in Qi State between the Spring and Autumn Period and the Warring States Period (770-221 B.C. ), has undergone much research and examination.

According to the research, the east side of the Great Wall is the city’s earliest checkpoint.

In the 1990s, some enthusiasts measured the wall and announced it was 618.9 kilometers long. According to the recent research, the wall is longer, but the figure will be announced, said Li Zhenguang, leader of the investigation team.

“One of the most significant discoveries is that Qingdao’s earliest checkpoint was located in what is now the Zuoguan ruin in Huangdao Island,” said Li Jufa, an expert from Huangdao Island Cultural Relics Management Institute.

Ancient buildings had been found in Xin’an, which meant the Anling City in Qi State was located in Qingdao.

“The Great Wall was used to defend against Chu State. In peacetime, it was an important trading channel. Zuoguan was a gate built in Anling, similar to what we would know as customs,” said Li.

The wall stretches from Changqing Township in Shandong Province to Huangdao Island in Qingdao via 18 cities and counties and is about 2,400 years old. It is of great interest to historians. (Wang Yuanyuan, Liu Hailong)