Engineering workers have discovered ridges on the groundsill of many buildings of Potala Palace during the phase II maintenance and total 140 ridges have been discovered since the project opened in 2002.

20 ridges were dicovered in the phase I maintenance and now 140 ones have been discovered in phase II, it's possible that more ridges would come out according to the section chief of Potala Palace Administration Office.

Those ridges were designed and built on the groundsill of Potala Palace buildings, which is believed to be built to prevent the buildings from sliding down from the slope of mountains by using aerodynamic force.

Potala Palace is a set of buildings without blueprints. It's featured unique architecture style. Nobody knows how many ridges have been placed in the groundsill of Potala Palace, the section chief added.

The Potala Palace is located on the mountians with an altitude of 3,763 meters. It's the largest existing castle buildings set at present in Tibet. It was listed on the World Cultural Heritage Directory by UNESCO in 1994.