Gyeongju was the capital of the ancient kingdom of Silla (57 BC – 935 AD) which ruled most of the Korean Peninsula between the 7th and 9th centuries. A vast number of archaeological sites and cultural properties from this period remain in the city. Gyeongju is often referred to as "the museum without walls". Among such historical treasures, Seokguram grotto, Bulguksa temple and Gyeongju Historic Areas are designated as World Heritage Sites by UNESCO.The many major historical sites have helped Gyeongju become one of the most popular tourist destinations in South Korea.