Which New7Wonders site is a series of fortifications built across northern China?

The New7Wonders site that is a series of fortifications built across northern China is the Great Wall of China.

The Great Wall is not one continuous wall built at one time. It is a vast defensive network of walls, trenches, passes, watchtowers, and fortresses constructed by different Chinese states and dynasties. Some of the earliest sections date to the 7th century BC, while the best-preserved sections were built or rebuilt during the Ming dynasty, from 1368 to 1644.

The fortifications protected northern borders, especially against forces from the Eurasian Steppe. Watchtowers supported smoke and fire signals, while garrisons and passes helped control movement and trade. The total surviving and documented system is estimated at about 21,196 kilometres, although the exact boundaries depend on what is counted as part of the Great Wall.

A common misconception is that the wall can be seen clearly from the Moon; it generally cannot be distinguished with the unaided eye from that distance. The Great Wall became a UNESCO World Heritage Site in 1987 and was selected as one of the New 7 Wonders of the World in 2007.