The legend of “Cẩu chủa cheng vùa” is about the establishment of Nam Cuong State, the rule by King Thuc Che and his son Thuc Phan, who later became the King of Au Lac united State, then moved the capital to Co Loa in present-day Hanoi’s Dong Anh District. On the other hand, the legend authentically describes the land of Cao Bang, with a flat valley in the center, surrounded by ranges of mountains. A series of places in the ancient Ban Phu Citadel were also described through the legend, reflecting the perceptions of the ancient people about natural landforms.
According to the legend of “Cẩu chủa cheng vùa”, the land of ancient Cao Binh was located along two sides of the Bang Giang river with Hoa An basin at the center. It includes 10 regions (9 villages and 1 center). The center village was ruled by Thuc Che, with title of An Tri Vương, who established Ban Phu Kingdom and the capital Nam Binh. It was surrounded by the other nine regions, the so-called vassal states governed by the lords named: Tien Dat, Kim Dan, Van Thang, Ngoc Tang, Thanh Giang, Quang Thac etc. They together established the Nam Cuong State, which was contemporary with Van Lang State of Hung Kings and the Lac Viet people in the South. After 60 years on throne, Thuc Che King died at the age of 95 when his son Thuc Phan was only 10 years old. The nephew of Thuc Che, named Thuc Mo, helped Thuc Phan in the regent, but as he abused power of the King, all nine regional lords were disobedient. They pulled troops to the center in order to force Thuc Phan subdivide the national land, and asked him to abdicate the throne of “the king”. Though, Thuc Phan was young, but very smart. He organized talent competitions with promise to abdicate the throne to the winner.
The talent competitions were organized with stratagems. They were all very difficult and time-consuming, such as shooting falling Banian leaves, making 1,000 needles from a plowshare, and even with “beauty trap” by assigning 10 beautiful young ladies to accompany the competitors etc., consuming much of time and efforts. They were so hard that none of the competitors could complete their competitions and therefore the lords had to submit to King Thuc Phan.
According to the legend, Ban Phu Citadel was located on a large area surrounded by rivers and fields in the nowadays Hung Dao Commune, Cao Bang City. This was the imperial court of the Palace during Thuc Che-Thuc Phan Dynasties and even the later Mac Dynasty. At that time, the military castle was based in Na Lu (the present-day Hoang Tung Commune, Hoa An District).
Ban Phu Citadel was built in a very beautiful location that faced to the Southeast. At the front of the Citadel was a 7ha-wide lotus lake and Cao Binh Plain, followed by the Tong Chup field. The field was initially called Tong Quang field to infer a large field, but later the name was changed to Tong Chup to refer to a story about the competition of Tien Dat Lord, who could not complete cultivating the entire rice field leaving an area “as tiny as a hat” unfinished. Close to the foot of the inner wall was a jade well (now called Bo Pho) that had clear water for all year round. Near the Lotus Lake were the Giao and Thien Thanh temples, which were rumoured as the places where the King worshiped the God. On the right and left sides of the wall was Peach garden (Dao Vien) of the Queen’s palace, namely Dong Tam, next to the resident place of maidens. The upper part of the hill, namely Thom Dang, was used to raise elephants. The kid area was called Ho Nhi or kid’s lake. Near Ban Phu, there was an ancient banyan, which was a place where Kim Dan Lord used his bow and arrows to shoot almost all the falling banyan leaves. Out of the outer wall, near Dau Go, there was a pair of giant stone clogs incompletely perforated to pierce straps, as a result of Van Thang Lord’s competition. Riding about one more kilometer along Highway No. 4, on the right side of the road appeared a hill called Khau Lua, i.e. boat hill, which tells a legend about the boat that Ngoc Tang Lord had yet to complete turning upside down. Opposite to Khau Lua, on the other side of Bang Giang river bank was Na Lu Citadel (with the King Le’s temple and festivals celebrated annually on 6th lunar January), which still lack a gate, as an unfinished work at the talent competition by Thanh Giang Lord. The other lords competing to write poems or make needles all failed because when the contest was almost completed, they heard the drum sound of Quang Thac Lord and supposed that he had won. In fact, Quang Thac also failed due to the “beauty trap” of Thuc Phan that dropped his drum rolling down the abyss and made echo of the noise. The place where the drum rolled down was named as Tong Lan.