Aerial photo of the first excavation site
Thanh Den Citadel in Chi Phong village, Truong Yen commune, Hoa Lu district, is an earthen citadel connecting natural stone mountains, forming a defensive line north of Hoa Lu Citadel.
Thanh Den consists of two sections: The first section connects from Sau Cai mountain (also known as Ham Xa mountain or Co Dai) to Canh Han mountain, this is the longest section of the wall of Hoa Lu capital, with a length of 500m; The second section from Canh Han mountain to Hang To mountain (also known as Nghen mountain), is a secondary wall section on the same line as Thanh Den, 150m long.
Site plan before excavation
During the excavation that took place from March 2025, the Institute of Archaeology opened two large excavation pits with areas of 450m² and 150m² respectively.
Archaeologists have clearly discovered a three-part structure: foundation, body and reinforcement layer, reflecting the technical level of citadel construction of the Vietnamese people in the early period of independence.
Cross section of soil and leaf layers for wall foundation and soil regeneration
First, they dug up a layer of soil and placed a layer of branches on top of it. Then, they created the foundation of the wall by stacking layers of clay and other materials. On top of this foundation, they built two perimeter walls to form the core of the wall, and placed a layer of white clay on top. This white clay originated from the sea, so it had a very flexible structure.
The body of the rampart has a trapezoidal or semicircular cross-section, in which the outer slope is given a greater slope, combined with layers of broken bricks and stones on both sides to prevent erosion.
10th century wall
Regarding the role and function of the wall, researchers found that the wall was not too high compared to other areas.
However, this fits in with the surrounding terrain and natural environment, as the area outside the wall is a vast marshland. Using this terrain to enhance defense capabilities is a notable point.
Regarding the history and construction process, researchers hypothesize that this wall may be related to King Le's war with Champa. After the victory, King Le captured prisoners to build defense works, including this section of the wall. The evidence is
Traces of the layers of the Dên Citadel Wall
Experts say the construction techniques at Den Citadel Wall have clear similarities with previously excavated structures such as Dong Tuong (1969), Den Citadel Wall (2018), and Dong Bac Wall (2024).
This is evidence that a unified, interconnected system of ramparts was formed, contributing to firmly consolidating the defensive role of Hoa Lu Capital from the North.
In addition, many relics were found such as broken bricks with letters, pieces of ceramic glaze from the Tran - Le dynasties, porcelain, mollusk shells, etc., which contributed to determining the age of the construction and affirming its continued use through many dynasties.
Some bricks with ancient inscriptions and red-covered bricks – commonly found in the 10th century – further strengthen the hypothesis about the initial construction period of this section of the citadel.
Ceramic vase from the 9th-10th century discovered in an excavation pit
At the workshop, 5 opinions were presented, focusing on clarifying issues related to the construction techniques, cultural stratigraphy, as well as the historical value of the relic in the overall Hoa Lu Capital.
In particular, experts highly appreciated the excavation work which was carried out methodically, in full compliance with archaeological research procedures; documents, photos and current drawings were fully archived, in addition to the application of 3D digital technology to reconstruct the excavation pit for in-depth research.
Based on the preliminary results and comments at the workshop, the working group will promptly complete a summary report to submit to the Ninh Binh Provincial People's Committee and the Ministry of Culture, Sports and Tourism.
Specialized agencies are also developing a proposal for an investment project to preserve, restore and renovate the Den Citadel relic, in conjunction with the development orientation of local tourism and cultural industry.
The workshop emphasized the role of communication and education in spreading heritage values and raising public awareness of the responsibility to preserve and promote historical and cultural relics.
Source: https://baovanhoa.vn/van-hoa/giai-ma-ky-thuat-thanh-quach-the-ky-x-tai-thanh-co-hoa-lu-doan-thanh-den-142673.html
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