The Great Wall of Qi is the oldest existing Great Wall in China. Construction of the wall started in 685 BCE (during the Spring and Autumn Period) by the state of Qi, to defend itself against an invasion by the Kingdom of Chu. The existing sections date back to 500 BCE. Construction ended during the Warring States Period.
The wall stretches from the areas under the administration of the present-day city of Jinan to the present-day city of Qingdao across the present-day cities of Tai'an, Zibo, Laiwu, Weifang, Linyi, and Rizhao. Its total length has been estimated at about 600 kilometers.