Việt Trì
Starting from the third Hùng dynasty since c. 2524 BC, the kingdom was renamed Văn Lang, and the capital was set up at Phong Châu (in modern Việt Trì, Phú Thọ) at the juncture of three rivers where the Red River Delta begins from the foot of the mountains. The evidence that the Vietnamese knew how to calculate the lunar calendar by carving on stones dates back to 2200–2000 BC. Parallel lines were carved on the stone tools as a counting instrument involving the lunar calendar.