These crowns were excavated in Gyeongju, the former capital of Silla, and are designated National treasures of South Korea.
The Silla crowns are very fragile and weigh more than one kilogram. The Silla kings probably did not wear the golden crowns regularly. They were probably used only for formal and ceremonial occasions.
The Silla crowns were uncovered in the tumuli of Gyeongju, South Korea, the capital of Silla and Unified Silla. Silla tumuli, unlike their Baekje and Goguryeo counterparts were made inaccessible because the tombs did not include passageways and corridors. Instead, deep pits were dug and lined with wood and this is where the treasures and coffin were placed. These burial pits were covered in dirt and sealed with clay and then the surface was covered with massive river boulders which were then covered with massive mounds of dirt. The heavy boulders also served to push the tombs deeper into the ground, thus making them even more inaccessible. The Silla burial mechanism made it so that grave robbers and foreign invaders could never steal their precious contents. Some of the crowns are made of pure gold and were probably reserved for kings. Other crowns have been discovered made from gilt-bronze or gold-plated bronze, probably for princes or lesser kings. Silla crowns have been excavated from the 5th century Gold Crown Tomb, and the 6th century Gold Bell Tomb and Heavenly Horse Tomb. The adoption of Buddhism by the Silla kings in 528 A.D. led to the eventual decline of the practice of burying gold artifacts in tombs and by the end of the sixth century the practice had stopped.
According to wikipedia