What is the longest wall in the world?

The Great Wall of China is the longest wall in the world. The complete defensive system, including trenches and natural barriers, measures about 21,196 kilometres according to a 2012 Chinese survey.

The Great Wall is not one continuous structure built at one time. Different Chinese states constructed walls from the 7th century BCE onward, and later dynasties connected, rebuilt, and extended them. The best-preserved sections were built or strengthened during the Ming dynasty, from the 14th to the 17th centuries.

Its purposes included protecting agricultural settlements, controlling movement, and managing trade along routes near the northern frontier. Watchtowers and beacon towers allowed messages to travel rapidly using smoke and fire signals.

A common misconception is that the wall can be seen from the Moon with the naked eye. It generally cannot. The Great Wall was designated a UNESCO World Heritage Site in 1987, and its many surviving sections vary greatly in condition and construction material.