考古学：中央アジアにあった2つの中世都市の物語

Two archaeological sites located over 2,000 m above sea level in the mountains of Uzbekistan are revealed to have been major urban centres, according to a new analysis published in Nature. The discovery of the remote sites, positioned along Asia’s medieval Silk Routes, may warrant a rethink of the role of peripheral communities in shaping trade and political interactions along the Silk Road.

Urban centres are rarely located over 2,000 m above sea level, with only 3% of the planet’s population living at or above that height. Archaeological cities located at this height are seen as unique given the technological limitation to building settlements and farming at that altitude. Tashbulak and Tugunbulak are two ancient cities located 5 km apart in the mountains of Uzbekistan, which were discovered in 2011 and 2015, respectively. Although both were located along Asia’s medieval Silk Routes, which were active throughout the medieval period (6th–11th centuries), previous research has revealed sparse evidence of large permanent communities at such altitudes.

Michael Frachetti and colleagues analysed data from 22 lidar (light detection and ranging, a remote sensing method) flights over Tashbulak and Tugunbulak, taken in July 2022. They found that Tugunbulak occupies approximately 120 ha (1.2 km2) and shows evidence of over 300 unique structures, which vary in size from 30 to 4,300 m2. More specifically, the researchers identified watchtowers connected with walls along a ridge line, evidence of terracing, and a central fortress surrounded by walls made of stone and mudbrick.

Tashbulak, meanwhile, occupies 12–15 ha (0.12–0.15 km2). Frachetti and colleagues note that even the smaller city follows urban planning similar to concurrent cities in medieval Central Asia, namely including a centre citadel made of an elevated mound surrounded by dense architecture and walled fortifications. They suggest that there are at least 98 visible habitations, which share a similar shape and size to those in Tugunbulak, and hypothesize that both cities were built to exploit the surrounding mountain terrain for defence as well as the abundant ores and pastures the highland region provides.
The authors conclude that their lidar flights offered them a more comprehensive view of the two ancient cities and note that further investigation of mountain cities such as Tashbulak and Tugunbulak can help to shed light on their impact on the social and political structures of the time.