Originally established as a sanctuary for the emperor, the caves gradually became a site of worship for locals.
In the 18th century, however, they fell into neglect and were largely forgotten until 1908 when Ernst Boerschmann, a visiting German architect, "discovered" the grand caves filled with Buddha statues, embossed artworks, and frescos.
Foreign art historians and collectors visited the site but it was not until 1921 that Japanese archaeologist Sekino Tadashi's photographs brought global attention to the grottoes.
Unfortunately, international art dealers, thieves, and smugglers descended on the unprotected treasure trove.
Between 1924 and 1925, thieves vandalized and looted the caves, bribing corrupt monks to break over 240 statues into fragments for sale. One of the major smugglers was Japanese art dealer Sadajiro Yamanaka, who exploited the chaos of World War II to sell stolen artifacts to Western buyers.
The prized item for sellers and collectors was the Buddha's head but the statue's other parts were sometimes sold separately in other countries.
About 120 statues located abroad are confirmed to be from Tianlong Mountain, making it one of the most damaged cultural sites in China, said Jia Chen, vice president of Taiyuan Cultural Relics Protection Research Institute.
"The grottoes are important cultural memories of Chinese history," he said. "The period when the grottoes were established marks an important phase in the localization of Buddhist cave art in China.
