The historical and archaeological site of Hac Y, in Tan Linh commune, Luc Yen district, was discovered in 1995. This is a complex of religious and belief architectural relics of communal house - temple - pagoda and other auxiliary works including Than Ao Den mountain (Hac Y), Hac Y pagoda, Dong pagoda, Dai Cai temple, Thuong Mien pagoda, Ben Lan pagoda, Ao Vua, and Racecourse, spread over an area of about 2km2.
Through many excavations, archaeologists discovered in this relic complex many artifacts with shapes and ages similar to those excavated in the Imperial Citadel of Thang Long - Hanoi such as: Bricks, tiles, stone pillars, Bodhi leaves, lotus, chrysanthemums, terracotta statues of various mascots such as dragon heads, phoenixes... along with worship objects, ceramics dating from the Tran Dynasty (13th-14th centuries). Historical scientists believe that this is a large-scale Buddhist architectural complex and is considered the "Imperial Citadel of Yen Bai".
In 2001, the Black Shirt Relic was recognized as a national historical and archaeological relic. However, due to the impact of storm No. 3, many structures and items of this relic complex were severely damaged.
On December 23, speaking to reporters, Mr. Trieu Van Huan, Head of the Department of Culture and Information of Luc Yen district, said: "The People's Committee of Yen Bai province has just approved the investment project to build a project to restore and embellish this relic with a total investment of nearly 22 billion VND.
The project will be implemented over 3 years. In the immediate future, the province will renovate and restore Dai Cai Temple and Pagoda, expected to be completed by the end of 2025.
According to Mr. Huan, every year on January 16, local people and many tourists come to offer incense to express their respect to their ancestors who taught people to open mountains and establish villages, and pray for favorable weather, good crops, national peace and prosperity.
