At the time, Nguyen dynasty assigned Thu thong Che Dong Duc Luan to direct 1.000 soldiers participating in building Tang Thu Lau. The structure was scientifically designed to ensure its function as a storage of important royal documents. To avoid fire and protect national original documents, it was built on an island located at the middle of the lake called Hoc Hai. The large two-story structure was made of brick and stone, roofed by tiles. Its walls were 0,4m thick. On the upper floor, there are 7 compartments, 2 wings and several doors. Railings can be found around the structure to avoid humidity. The lower floor was divided into 11 compartments and also surrounded by railings. Tang Thu Lau was the place where documents of diplomatic agencies and ministries were stored.
After Tang Thu Lau had been completed, Emperor Minh Mang constructed a stele to record its purpose, function and meaning. Over time, Tang Thu Lau performed several different functions, therefore, its structure was partly damaged. The stele previously constructed by Emperor Minh Mang also disappeared. The entire structure was seriously degraded. In 2014, the project on renovating Tang Thu Lau was approved by competent agencies. Today, the construction was completed and officially put into use.
Tang Thu Lau - Hoc Hai lake was recognized as a national art architecture on Decision 99/2004/QD-BVHTT dated December 15th, 2004 of the Ministry of Culture and Information./.