Thanh Nha Ho (Citadel of Ho dynasty) first was the Tran dynasty's imperial city from 1398 to 1400, and then it was the Ho dynasty's imperial city until 1407. From the time of Ming's invasion until late l6th century is constantly played the role of a military base, a political, economic, and cultural centre of various dynasties of political powers in the Central Vietnam.Thanh Nha Ho was well planned on a large scale with two citadel enclosures: internal Hoang Thanh (Imperial Citadel) embracing the whole imperial city (La thanh). Outside of it was Xa Tac open-air altar to the west and Nam Giao open-air altar to the south. Outside the four Gates of the citadel was streets and citizen accommodation. Hoang Thanh is the most typical architecture of the Ho dynasty, with outer wall built with huge rocks and inner wall built with earth and pebble mix, which was surrounded by moat. From the North Gate through the south Gate to Nam Giao open-air altar, there are traces of 4m-wide road built with rocks. Thanh Nha Ho is a cucumber and unique architecture, demonstrating the combination of original talents and Oriental idea and tradition of Vietnamese people, which creates one of the most outstanding historical and cultural values of Mankind.