The events associated with the construction of this spiral-shaped citadel have been remembered in the legend of the golden turtle. According to this legend, when the citadel was being built, all the work done during the day was mysteriously undone during the night by a group of spirits seeking to avenge for the son of the previous king. The local spirits were led by a thousand-year-old white chicken perched on nearby Mount Tam Đảo. The King then burnt incense, prayed, and evoked the gods to help him. In answer to his plea, a giant golden turtle suddenly emerged from the water, subdued the white chicken, and protected him until the citadel's completion. When he departed, he gave one of his claws and instructed the King to use it as a trigger of a crossbow, with the assurance that with it he could be invincible.