Every year, activities worshipping Lac Long Quan and Au Co take place ahead of the commemoration of the Hung Kings, believed to be the very first founders of Vietnam, on the 10th day of the third lunar month (which falls on April 10 this year).

Since April 1, Phu Tho has organized a range of cultural and sport activities on this occasion.

Legend has it that Lac Long Quan (real name Sung Lam, son of Kinh Duong Vuong and Than Long Nu) married Au Co (the fairy daughter of De Lai). Au Co then gave birth to a pouch filled with 100 eggs, which soon hatched into a hundred sons. However, soon thereafter, Lac Long Quan and Au Co separated. Lac Long Quan went to the coast with 50 of the children, while Au Co went to the highlands with the rest.

Their eldest son was made king, who named the country Van Lang and set up the capital in Phong Chau (modern-day Viet Tri city in Phu Tho province), beginning the 18 generations of the Hung Kings.

The kings chose Nghia Linh Mountain, the highest in the region, to perform rituals devoted to rice and sun deities to pray for healthy crops.

To honor their great contributions, a complex of temples dedicated to them was built on Nghia Linh Mountain, and the 10th day of the third lunar month serves as the national commemorative anniversary for the kings.

The worship of the Hung Kings, closely related to the ancestral worship traditions of most Vietnamese families, was recognized as part of the Intangible Cultural Heritage of Humanity by UNESCO in 2012./.