Core Viewpoint - The article discusses the historical significance and restoration efforts of the Tianti Mountain Grottoes, particularly focusing on the Great Buddha Cave, which has faced challenges due to water damage and historical alterations [1][6][21]. Group 1: Historical Significance - The Tianti Mountain Grottoes are recognized as the first royal grottoes in China, directly commissioned by a king during the Northern Liang period, showcasing early grotto art [2][3]. - The site contains over a hundred statues and hundreds of square meters of murals, along with valuable texts and artifacts from various dynasties [2][3]. Group 2: Relocation and Preservation Efforts - In 1958, the local government decided to build a reservoir, threatening to submerge the grottoes, leading to a large-scale relocation effort approved by the Gansu provincial government [4][6]. - The relocation involved moving 43 statues and 300 square meters of murals to the Gansu Museum, while the Great Buddha Cave was left in situ due to the size of its sculptures [4][6]. Group 3: Restoration Challenges - The Great Buddha Cave's sculptures suffered significant water damage, with parts submerged for over 30 years, leading to erosion and loss of structural integrity [6][21]. - Restoration efforts began in 1995, utilizing modern materials while adhering to the principle of "repairing the old as the old" despite limited historical references [19][21]. Group 4: Restoration Techniques - The restoration team, led by Li Yunhe, employed innovative techniques, including the use of steel reinforcements for the sculptures' frameworks, replacing the original wooden structures [15][19]. - The team faced the challenge of reconstructing the Buddha's head using only black-and-white photographs from the 1950s, which required significant scaling and artistic interpretation [13][14]. Group 5: Legacy and Impact - Li Yunhe's dedication to the restoration of the Tianti Mountain Grottoes has inspired a new generation of conservators, with his family continuing the tradition of cultural heritage preservation [21][23]. - The successful restoration of the Great Buddha Cave has garnered praise from experts and the public, highlighting the importance of cultural heritage conservation in China [21].