This paper examines the city planning system of the ancient Bohai State using recently declassified intelligence satellite (CORONA satellite) photos acquired in the 1960's by the United States. Based on the reconstructions made in my recent report, I tried to make clear some principles shared by those city planning. It is also intended to prove the usefulness of satellite images in historico-geographical and archaeological applications.
The Bohai State was a kingdom which existed from 698 AD to 926 AD in the northeastern part of today's China (Fig. 1). It was formed by the Tungusic people in association with refugees from Koguryo, which had fallen in 668. It actively imported Chinese culture and political system and boasted high standard of civilization. While bringing tribute to Tang China, it dispatched envoys to Japan many times across the sea. Since records by Bohai itself had been lost, we can only obtain a glimpse of its prosperity through Chinese histories and records in Japan concerning envoys as well as archaeological evidence. Xin-Tang-shu, a history of Tang China compiled in 1060, praised Bohai as "a thriving country eastward across the sea" which has "five capitals".
Five capitals of Bohai referred to in Xin-Tang-shu includes Shangjing Longquanfu (Northern Capital), Zhongjing Xiandefu (Central Capital), Dongjing Longyuanfu (Eastern Capital), Nanjing Nanhaifu (Southern Capital) and Xijing Yalufu (Western Capital). Dongjing was also referred to as the gateway to Japan. Among these capitals, Shangjing (Ning-an, Heilongjiang Province), Zhongjing (Helong, Jilin Province) and Dongjing (Hunchun, Jilin Province) were researched and identified by Japanese archaeologists in the 1930s and the early 1940s. From the reports of these researches, it is known that Shangjing is the most important ruin having triply nested structure consisting of rectangular innermost, inner and outer city and grid-pattern streets. This method of planning was borrowed from China's capital Chang-an and shared by the capitals of Korea and Japan of that period. As for Zhongjing and Dongjing, remains of rectangular inner cities were evident, but existence of outer city and grid-pattern streets has been questioned.
Based on my recent report, remains of the plans of Shangjing, Zhongjing and Dongjing were reviewed using satellite photos. Shangjing was said to be the king's capital of Bohai for the longest time. From the satellite photo over Shangjing (Fig. 3), remains of the rectangular city walls and grid-pattern streets are very clear, reconfirming that it is the most important among the ruins of Bohai State. It is evident that main street from the palace gate to the main city gate is of considerable width. Among the lateral streets, the street adjacent to the southern side of the Palace site (innermost city) seems to be wider than the others. It demonstrates typical city planning shared by the East Asian ancient states. Fig. 2 shows my reconstruction of Shangjing using satellite photos.
Zhongjing was said to be the king's capital for a short period circa 750. The existence of outer city wall and grid-pattern streets around the already-known inner city was examined using satellite photos over Zhongjing (Fig. 5). Patterns of fields and snow marks show the remains of the main street and the lateral street along the southern side of the inner city. Patterns of the canals also suggest the traces of the outer city wall. From these traces, reconstruction of the whole city is presented (Fig. 4).
Dongjing was said to be the gateway to Japan and the king's capital for a short period circa 790. However, Japanese records on the dates and places of arrival of envoys from Bohai to Japan show that the origin of the voyage moved to Nanjing circa 820. From satellite photos over Dongjing (Fig. 7), remains of the main street and two lateral streets are evident outside the already-known inner city. The outer city wall seems never to have been constructed. The most outstanding feature of this plan is the enormous width of the main street (190 meters) and one of the lateral streets (130 meters) (Fig. 6).
In recent studies in China by Liu Xiaodong and Wei Cuncheng it was hypothesized that the plan of Shangjing of a triply nested structure reflects the historical stages of expansion. They pointed out that the innermost city of Shangjing seems to be based on a similar design to inner cities of Zhongjing and Dongjing. The CORONA Satellite photos also show that the designs of the innermost area of Shangjing and the inner city of Zhongjing are identical (compare IJKL in Fig. 3 and ABCD in Fig. 5). This method of planning can be attributed to the reign of Da Qinmao, the third king (r. 738-793).
One of the features shared by Bohai cities is the extreme width of the main street and the lateral street along the southern side of the inner city. This can be partly explained by the fact that these plans and buildings on them were displays. Da Qinmao exchanged envoys with the Japanese emperors many times, but there seems to have been conflict about which should pay homage. Japan's capital of the same time (Nara) also had grid-pattern streets and a wide main street. From the reconstruction using aerial photos over Nara, it is known that the city blocks near the main street were selectively well constructed. Being displays to foreign visitors to show off the power of the country could be a common feature shared by the East Asian capitals of that time.
Bohai is sometimes referred to as the successor of Koguryo. In Koguryo, it is said that hill-forts were located near cities and important places. Stereoscopic satellite photos on Fig. 8 show a typical example of hill-forts in the northeastern China, which has a wall along circularly concatenated ridges and concave interior. It has been suggested that this hill-fort was constructed by Koguryo and continued to be used by Bohai and subsequent dynasties. Another example of hill-forts is identified on the satellite photos, which is located 5 kilometers southwest from the ruin of Zhongjing (Fig. 9). Comprehensive research of location and structure of hill-forts in Bohai remains the subject to be addressed.
The city planning system of Bohai may be characterized as of a "conspicuous" nature as well as those of other East Asian nations of the same age. While being a close follower of Chinese political and cultural systems, Bohai might have maintained the indigenous culture such as hill-fort system, which is peculiar to the region covering northeastern China and northern part of the Korean peninsula.
Key words: historical landscape, satellite photo, Ancient East Asian City Planning, The Bohai State, hill-fort
(Jinbun Chiri, Vol. 52, No. 2, 2000, pp.129 - 148)