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Chinese President Xi Jinping has sent a congratulatory letter to the Science and Technology Daily on the occasion of the 40th anniversary of its founding.
The Xi'an City Wall, initially built around 1,400 years ago in 582 AD during the Sui dynasty, now extends 13.74 kilometers, surrounding the ancient city of Xi'an in Shaanxi province, north-west China. As one of the oldest, largest and best-maintained ancient city fortifications in China, the wall has faced significant preservation and protection challenges. This is because its inner structure, primarily made of tamped earth, has eroded over time due to the elements.
