Below is an instruction that describes a task. Write a response that appropriately completes the request.

### Instruction:
Provide a short description of the great Wall of China

### Response:
The Great Wall of China is a series of fortification systems built along the historical northern borders of China to protect and consolidate territories of Chinese states and empires. It was originally built by the First Emperor of China in the 7th century BC, and later rebuilt and maintained between the 5th century BC and the 16th century. With a total length of over 21,000 kilometers, it is the largest human-made structure ever built and is listed as a UNESCO World Heritage Site. The wall featured watch towers at regular intervals. In more recent times, it has become a popular tourist attraction and has also been used for scaffolding by construction workers in some portions.