The building of Seokguram Grotto was started in the 10th year of King Gyeongdeok of Silla (751) by Kim Dae-seong, who was one of the highest officials titled ‘Daesang’ at the time, and completed in the 10th year of King Hyegong (774). At the time of its construction, it was called Seokbulsa Temple. King Gyeongdeok was a king of the mid-Silla Dynasty, and during his reign (742-765), Silla`s Buddhist art reached its peak. In addition to Seokguram Grotto, many cultural assets such as Bulguksa Temple, Dabotap Pagoda, Three-story Stone Pagoda, and Hwangnyongsa Temple Bell were built at this time.A stone cave was artificially created using white granite on the mid-slope of Mt. Toham, and a total of 40 Buddha statues, including statue of Bodhisattva, statue of disciple, statue of a Deva king (a man of great strength), and statue of heavenly kings, were carved on the walls around the main Buddha statue, Sakyamuni Buddha, in the interior space, but now only 38 statues remain.The structure of Seokguram Grotto is that the rectangular front chamber, which is the entrance, and the circular main chamber, are connected by a passage that serves as a corridor, and the architectural technique of skillfully constructing the ceiling of the circular main chamber with 360 flat stones is an outstanding technology unprecedented in the world. In the front chamber corresponding to the entrance of the Seokguram Grotto, there are statues of four of the eight guardians of Buddhism on the left and right sides, respectively, and statues of Deva kings, men of great strength, were carved at the left and right entrances of the aisles, and two statues of the Four Heavenly Kings were carved on the left and right sides of the narrow aisles, respectively, each protecting the four directions. At the entrance of the circular main chamber, octagonal stone pillars are placed on the left and right sides, and the Sakyamuni Buddha is enshrined slightly behind the center of the main chamber. The walls of the main chamber are filled with 2 Cheonbu, 2 Bodhisattva and 10 Arhat(Buddha`s disciples) statues from the entrance, and on the round wall behind the Sakyamuni Buddha stands the most elaborately carved Eleven-faced Avalokitesvara Bodhisattva statue in the cave.The Sakyamuni Buddha perfectly shaped with mature sculpting techniques and realistic expressions, the Eleven-faced Avalokiteshvara Bodhisattva statue with gorgeously carved face and body, statue of the courageous two Deva kings (the guardian gods of a temple gate), the majestic Four Heavenly Kings statue, various bodhisattva statues with flexible and graceful appearances, and Arhat(Buddha`s disciples) statues, each with a unique expression, etc., all the sculptures made here are comparable to the best masterpieces of Buddhist sculpture in East Asia. In particular, the tranquil appearance of the Sakyamuni Buddha enshrined in the main chamber adds to the depth of mystery in the secret atmosphere of the entire grotto. The extremely natural figure of the Sakyamuni Buddha is the most ideal figure with a deep and noble heart inside, and compassion seems to be naturally conveyed to all human beings.As Seokguram Grotto is the greatest masterpiece created during the heyday of Buddhist art in the Silla Dynasty, it stands out because it organically combines architecture, mathematics, geometry, religion, and art. Seokguram Grotto is designated as a national treasure and managed, and Seokguram was jointly registered as a UNESCO World Heritage along with Bulguksa Temple in December 1995.Meanwhile, since 1976, Seokguram Grotto has only been viewed from the outside through a glass wall due to concerns about constant temperature and humidity issues when viewing the entire interior of Seokguram.