Co Loa, Hoa Lu, and Thang Long used to be the imperial cities of many dynasties. From the perspective of planning and structure, they took thorough advantages of the natural conditions to set up uninterrupted fort-rings of advantageous battle-lines for defense and attack by both land and river. | The Scheme and Structure of Co Loa. THE SCHEME AND STRUCTURE OF CO LOA, HOA LU AND THANG LONG ANCIENT ROYAL CAPITALS LAI VAN TOI * Abstract: Co Loa, Hoa Lu, and Thang Long used to be the imperial cities of many dynasties. From the perspective of planning and structure, they took thorough advantages of the natural conditions to set up uninterrupted fort-rings of advantageous battle-lines for defense and attack by both land and river. They did not stickle much for the balanced shape by appearance, but they were based on important and advantageous features. All those imperial cities have fort-rings that follow the “threefort model”, including outer Wall, Royal City, and Forbidden City; each fort-ring undertakes particular functions with an appropriate layout in order to get the best protection for the king, royal families and the court. It is especially valuable that all these three ancient imperial cities left to us a lot of cultural – historic vestiges, which are full of vitality for now and future. Key words: Imperial city, Co Loa, Hoa Lu, Thang Long, planning, structure. 1. In Scheming In Co Loa Ancient Castle Nowadays, at Co Loa vestige area, there are three castle rampart circles which are Outermost Castle rampart, Middle Castle rampart and Innermost Castle rampart. These three castle rampart circles have been distributed in an area about 600 hectares, the circumference is 18,000 meters (the Outermost Castle). In the scheme, An Duong Vuong absolutely took advantage of the area’s natural conditions. As we have known, Co Loa was originally the alluvial ground of Red River belonging to the high Western part of the North Vietnamese delta, and lying completely in the water quadrilateral: Ca Lo river in the North, Duong river in the South, Red river in the West and Cau river in the East. Right at the foot of the Outermost Castle rampart in the South, there was flowing Hoang Giang river which was used as the outer trench. From Co Loa passing over Hoang Giang .
