The Bien Hoa ancient citadel is the only Site that is being preserved in the Southeast part of Southern Viet Nam. It has the same structure as the Vauban citadel in 1861 and its area is up to 1.1 ha, which is about from 1/7 to 1/8 of the Nguyen - period citadel. According to some Vietnamese historical books, the ancient citadel in Minh Mang Dynasty has a. flag tower, four doors and stone bridges on moats. Its area is approximately 1.8 hectares, which can be considered to be the largest among the other Southeastern citadels from the same period, except the Gia Dinh Citadel. On February 2012, in response to the Revolutionary People's Committee in B6ng Nai's request, the scientists from the Archaeological Section (the History Department - USSH-HCM City), collaborating with Dong Nai provincial Department of Culture, Tourism and Sports dug 14 pits for archaeological investigation at Bien Hoa citadel with the total area of 60m2, 3054 artifacts were found in the 90cm -140cm-thick cultural stratums from 3 sources directly related to the longterm inhabitants in this area. They includeo tiles with Buddha decorative, earthen stoves, various kinds of white pottery from the developing period of the Oc Eo culture (6th-7th centuries). The collections of bricks, terra-cotta wares, and household items such as glazed ceramics, stone-ware and blue-and-white porcelain shards originated from Bien Hoa, Lai Thieu, Sai Gon, Go Sanh, Champa, Khmer, Thailand, Southern China), bronze and stone bracelets etc. demonstrating the existence of original dwelling inhabitants from medieval to contemporary times (14th - 15th AD to 19th - 20th centuries). New archaeological findings of the Tan Lan ancient village from the lowest layers of Bien Hoa Citadel provide good data for the historical study of Dong Nai in particular and the Southern Viet Nam in general.