Mamluk-Era Tunnels Drove Sugar Mills of the Levant

How a Hidden Medieval Water System Turned Brackish Springs into Sugar Power

The turquoise pools of Gan Ha-Shelosha in northern Israel look like a postcard: bathers, palm trees, and sun on the water. What no one suspected was that a medieval industrial machine lay directly beneath their feet.

During recent infrastructure work in the Bet She’an Valley, engineers sliced into the banks of Nahal ‘Amal and exposed five clean-cut openings in the tufa rock. When archaeologists led by Prof. Amos Frumkin of the Hebrew University investigated, they found not natural caves but a carefully engineered underground water network dating to the late Mamluk period, roughly the 14th–15th centuries CE.

A hidden hydraulic engine

The openings led into low tunnels, carved with striking precision through soft tufa along the stream. Their gentle but consistent gradient, smoothed channel floors and flow marks made it clear that this was no refuge or secret passage: it was a hydraulic system built to move water under pressure.

Radiometric uranium–thorium dating of stalactites that began forming soon after excavation pinned the tunnels to the closing centuries of Mamluk rule. That was exactly when sugarcane cultivation boomed across the eastern Mediterranean—and when the Bet She’an Valley emerged as one of the region’s premier sugar districts.

Unlike the open stone aqueducts familiar from Roman and Byzantine sites, the Nahal ‘Amal channels were deliberately buried. Carving directly into the rock protected the water from evaporation in the hot valley, shielded it from contamination and, crucially, preserved the pressure needed to spin machinery downstream.

Hydraulic modelling of the slope and cross-section suggests that the tunnels fed water to horizontal paddle wheels. These in turn drove millstones that crushed harvested cane stalks in adjacent mills—heavy, noisy installations whose remains still dot the valley. A Mamluk oil lamp found at the base of one reconstructed mill, located just below the tunnels, anchors this reconstruction in the material record.

In short, the serene pools of Gan Ha-Shelosha were once the headwaters of an industrial belt.

The working of a southern Levant sugar mill. A. Reconstruction of a sugar mill, modified after Stern (1999). B Excavated sugar mill at Masna’ as-sukkar, as-Safi. After Jones (2015). 1—chute; 2—water wheel; 3—lower (or fixed) millstone; 4—upper millstone (or runner)

Sugar, state power and the 14th-century Mamluks

To understand why anyone would go to such an effort to harness a brackish spring, you have to zoom out from this quiet valley to the Mamluk Empire itself.

From 1250 to 1517, the Mamluk sultans ruled Egypt, Syria and Palestine from Cairo, first under the Bahri line and later the Circassian Burji dynasty. By the 14th and 15th centuries, this empire had weathered Crusader wars, repelled the Mongols at ‘Ayn Jālūt, and positioned itself as the middleman of Afro-Eurasian trade.

It was an era of contradictions. The Black Death hit Egypt and Syria hard, repeatedly slashing populations and disrupting agriculture. At the same time, Cairo and the coastal ports grew rich by taxing and controlling the spice trade that flowed from the Indian Ocean to Europe.

Sugar sat at the intersection of these forces. Cane cultivation had spread to Egypt centuries earlier, but under the Mamluks, it became the backbone of state revenue. Sultans and powerful emirs invested in estates, mills and irrigation, turning sugar into a state-backed cash crop whose production peaked in the 13th and 14th centuries before declining under the pressures of drought, internal unrest and competition from places like Cyprus.

In Egypt proper, plantations lined the Nile. In the southern Levant—today’s Israel, Palestine and Jordan—Mamluk officials invested in sugar estates in places such as the Jordan Valley and Bet She’an, integrating them into imperial trade routes linking Cairo, Damascus and the Mediterranean ports.

Medieval geographers like Yāqūt described Bet She’an as a sugar country whose products were shipped “to the entire East”. Archaeology has slowly caught up with those texts: ruined mills, processing complexes and the characteristic ceramic “sugar pots” used for refining have turned up across the region.

The Nahal ‘Amal tunnels now provide the missing upstream piece of that industrial system.

A Entrance to Tunnel F (photo: Yinon Shivtiel); B General view of Tunnel F. Note tunnel cross section, which differs significantly from those of the tunnels on the northern bank of the stream (photo: Azriel Yechezkel). Note actively flowing water; C Sharp bend in tunnel; in circle: hewn oil-lamp niche (photo: Azriel Yechezkel)

Turning bad water into good power

The springs that feed Gan Ha-Shelosha are picturesque but problematic. The water is slightly saline—unpleasant to drink and poor for irrigation. For a medieval engineer, that could look like a nuisance or an opportunity. The Mamluks clearly chose the second option.

By diverting the brackish flow into covered tunnels, they transformed otherwise marginal water into a reliable power source. The rock-cut channels carried the stream downhill with enough pressure to turn wheel shafts and millstones in the sugar factories below, leaving the more precious fresh water from elsewhere for people and crops.

Carving into soft tufa had other advantages: the stone was easy to cut yet strong enough to hold stable channels. The enclosed system also meant that sudden floods or seasonal variations in the open stream were damped out, providing fairly steady power to the mills during the crushing season.

This is not the monumental water architecture most people associate with the Mamluks—those soaring aqueducts, mosques and baths in Cairo and Damascus. It is infrastructure on a different scale: hidden, purely functional, and tightly adapted to local geology.

From sugar mills to flour mills

History rarely stops when one empire falls. When Ottoman forces absorbed the Mamluk domains in 1516–1517, they inherited not just cities and ports but an entire landscape of mills, canals and tunnels. Evidence from the Bet She’an Valley suggests that many of the Mamluk-era sugar mills were converted into flour mills under Ottoman rule while still relying on the same tunnelled water supply.

In other words, the tunnels under Gan Ha-Shelosha outlived the sugar boom that created them. As cane fields declined and global sugar production shifted elsewhere, the hydraulic system was repurposed rather than abandoned—a quiet example of technological continuity bridging two imperial regimes.

Rethinking “stagnant” medieval technology

The Mamluk tunnels of Nahal ‘Amal complicate a persistent stereotype: that the medieval Islamic East was technologically static while innovation flourished elsewhere.

Here we see 14th–15th-century engineers:

• reading a difficult landscape of saline springs and porous rock,

• choosing to bury canals rather than build showy aqueducts,

• and using flowing water not simply for irrigation but as industrial energy to drive one of the era’s most lucrative export industries.

It is a story about much more than tunnels. It links geology, hydrology, imperial policy and global commerce. Brackish water, carved stone and wooden wheels in a quiet valley were part of a network that stretched from the fields of Bet She’an to the markets of Cairo, Damascus and Venice.

Today, swimmers drift through the park’s warm pools, unaware that beneath them, medieval engineers once coaxed power out of “bad” water and fed it into mills that sweetened the tables of half a world.