 After assembling an army, he defeated and overthrew the eighteenth dynasty of the Hùng kings, around 258 BC.He then renamed his newly acquired state from Văn Lang to Âu Lạc and established the new capital at Phong Khê in the present-day Phú Thọ town in northern Vietnam, where he tried to build the Cổ Loa Citadel (Cổ Loa Thành), the spiral fortress approximately ten miles north of that new capital.However, records showed that espionage resulted in the downfall of An Dương Vương.