Location: Dien Khanh Citadel is situated on Dien Khanh Townlet, Dien Khanh District, Khanh Hoa Province.

Characteristic: The Dien Khanh Citadel was built by Nguyen Anh in 1793 with an area of 36,000 square meters according to the Vauban military architecture which was popular in Western Europe in 17th - 18th centuries

The citadel's wall was in an inequilateral hexagon of 3.5m height. The outer face was vertically constructed while the inner was a little bit sloping by two terraces forming a favorable pavement. Inside the corners, there were large fields which were convenient for military resident. On the top of corners there stood fortresses of 2m high with canons above. On the roof of the citadel, there planted clobamboo and other barricade trees. Surrounding the citadel were moats of 4 to 5 meters deep, 10 meters wide, flooded by water.

At first the citadel had 6 gates but nowadays it remains only 4 ones which are East Gate, West Gate, Front Gate (to the South), Back Gate (to the North). There had been here royal palace, private residents of feudal mandarins, warehouses and jails...

Dien Khanh is one of the oldest citadels in the south of Vietnam and it is one of the precious vestiges for studying ancient citadels.