A Stack of Fortresses
In the Kashkadarya region of Uzbekistan, part of the ancient Bukhara oasis, the remains of Uzun Kala fort present a deceptively simple picture on the surface. For centuries, this settlement was a strategic point along the caravan routes that crisscrossed Central Asia. What conventional archaeology could only reveal through slow, destructive excavation, a geophysical survey using ground-penetrating radar (GPR) mapped in high resolution. The survey showed that the visible ruins are the final layer of a long history. Beneath the ground lies a vertical stack of at least ten distinct occupation layers.
Ground-penetrating radar is a non-invasive technique that sends pulses of radio waves into the earth. When these waves encounter a change in material—such as the boundary between a mud-brick wall and the soil packed around it—they reflect back to a receiver. The time it takes for the waves to return allows scientists to map the depth, size, and shape of buried features without digging. At Uzun Kala, the GPR data revealed that the fortress was systematically demolished and rebuilt upon its own flattened ruins ten times. Each layer represents a completely new city, constructed on a slightly altered plan from the one it replaced.