Tibet's Potala Palace a vital project for conservation

Yang Na has many "patients".But she has been watching over a special one, roughly 3,600 km away from her, for over 15 years.

She is not a medical doctor but a professor of engineering in Beijing. Her special "patient" is the Potala Palace.

Located at the Red Mountain of Lhasa at an altitude of 3,700 meters in the Tibet autonomous region, the Potala Palace was built by Tibetan King Songtsen Gampo in the seventh century as an expression of his love for Princess Wencheng of the Tang Dynasty's (618-907).