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Beneath the verdant pools of Gan Ha-Shelosha lies a network of medieval tunnels that once powered the thriving sugar industry of the Mamluk Empire. Hewn into soft tufa rock along Nahal 'Amal, the tunnels reveal how medieval engineers transformed brackish spring water into a source of mechanical energy, adapting their methods to a dry landscape.

Radiometric dating and archaeological evidence suggest these channels supplied water to sugar mills, linking local ingenuity to the wider economic currents of the late medieval Mediterranean. The discovery redefines the industrial landscape of the Bet She'an Valley, highlighting an unexpected fusion of geology, hydrology, and commerce in the medieval Levant.

Deep beneath the sunlit pools of Gan Ha-Shelosha National Park, archaeologists have uncovered a forgotten infrastructure that may rewrite what we know about medieval industry in the Holy Land.

Led by Prof. Amos Frumkin of the Institute of Earth Sciences at the Hebrew University of Jerusalem, a multidisciplinary team has identified a network of water tunnels carved into soft tufa rock at Nahal 'Amal—structures that appear to have powered sugar mills during the Mamluk period (13th–15th centuries CE).

The findings are in the journal Water History.

The hewn tunnels, long hidden under modern development, were noticed when infrastructure work exposed five parallel openings. "Their engineering precision suggested a hydraulic purpose," Frumkin explains. "But unlike the open aqueducts typical of the era, these channels were subterranean—an adaptation to the valley's geology and the brackish nature of the local water."

Using uranium–thorium dating of stalactites formed soon after the tunnels' excavation, the team determined that they were likely constructed in the late Mamluk period, around the 14th to 15th centuries CE. This corresponds with the height of the region's lucrative sugar trade, when the fertile Bet She'an Valley was known as a hub for cane cultivation and export throughout the eastern Mediterranean.

Historical sources describe the Mamluks' mastery of water management—from aqueducts and baths to vast irrigation networks. Yet this study reveals how they also innovated with water energy for industry. Sugarcane production required constant irrigation and mechanical crushing, processes traditionally powered by channeled streams.

The tunnels of Nahal 'Amal likely served to drive horizontal paddle wheels that turned millstones to crush canes, converting the valley's brackish spring water into a source of mechanical power rather than irrigation.

Frumkin and his team—Azriel Yechezkel, Dror Segal, and Yinon Shivtiel—found that the tunnels' slope, flow traces, and location matched the needs of sugar mills rather than flour mills. A Mamluk oil lamp recovered in a downstream mill further anchors the site chronologically.

Over the centuries, these sugar mills were repurposed into flour mills during the Ottoman period, showing how water resources evolved with changing economies.

"This discovery bridges industrial archaeology and hydrology," says Frumkin. "It demonstrates that medieval engineers in the southern Levant adapted not only to scarcity but also to opportunity—turning brackish water into a sustainable source of power."

The study challenges assumptions that the arid Levant was technologically stagnant in the Middle Ages. Instead, it portrays the Mamluks as pragmatic innovators whose infrastructure sustained both local communities and international trade.

"Understanding these hidden tunnels helps us see the Mamluk world not just as a military empire," Frumkin notes, "but as one deeply invested in harnessing natural forces for economic resilience."