Thanh Nha Ho (Citadel of Ho dynasty) was built and existed as Ho dynasty's imperial city (Tay Do) in the late 14th century - early 15th century. In the history of Vietnamese monarchy, Ho Quy Ly was a great reformer, expressing high national spirit. After deposing the Tran dynasty and establishing the Ho dynasty, Ho Quy Ly built Tay Do which rapidly became a national political centre, a prosperous area of Vietnam. Thanh Nha Ho was a large-scale monument, especially Hoang Thanh (Imperial Citadel) and Nam Giao open-air altar. These two monuments were built with huge blocks of rock, which were very rare in the world. Its unique scale, architecture and construction technique are still incredible for researchers. Thanh Nha Ho certainly maintains a storage of rich and valuable relics and artifacts that need further research to improve awareness and serve the tasks of management, planning, preservation and valorization of the heritage values.