1. The Great Wall of China is one of the world's most iconic ancient wonders, stretching over 13,000 miles （21,000 km） from Shanhaiguan in the east to Jiayuguan in the west across diverse terrains 。

2. This monumental structure was built over centuries to protect China's northern borders from nomadic invasions, with sections dating back to the 7th century BC 。

3. The wall is made of a series of interconnected fortifications, including watchtowers, barracks, and garrison stations, designed to communicate military signals across vast distances 。

4. Today, the Great Wall is a UNESCO World Heritage site and a symbol of China's historical resilience, attracting millions of visitors annually 。