This castle was constructed in 101A.D. during the 22nd year of the reign of the 5th King Pasa-wang, to enclose the Silla palace and its grounds.
It is called Weolseong because, as the name implies, it is shaped like a crescent. It was also called Jaeseong which means the castle where the king resides.
Legend has it that before the castle was built a man called Hogong had lived there, but was chased away due to the magic of a young man named Talhae, who then made the place his home. When Namhae-wang(king) heard of this, he thought that the young man was no ordinary boy and took him as his son-in-law. The boy grew up to become the 4th king of Silla, Talhae-wang. The south river(Namcheon) flows along the south wall providing a natural barrier, and in the east wall is a gate. During the 1981 Weolseong excavations, it was found that the castle is encircled by a moat. The castle was geographically important.