The arrangement is unusual enough on its own, but what makes this site genuinely remarkable is how much of the working machinery remains: waterwheels, trip hammers, cisterns, guillotines, bellows mechanisms, and grindstones, most of it still sitting where it was last used when the complex closed in 1960.

The Beale family established the mills around 1790, and for the better part of two centuries the glen rang with the production of spades, shovels, and general ironwork. The four mills worked in a cascade. The uppermost pond, straddled by a railway viaduct, fed O'Hara's mill, an L-shaped forge hammer mill built on a rock-cut platform. Here, water delivered through cast-iron pipes to a wooden cistern powered two separate wheels: one an overshot cast-iron waterwheel that drove furnace bellows, the other a pitchback wheel that actuated a trip hammer via a cam mechanism. A trip hammer is a heavy forge hammer lifted and dropped repeatedly by the rotation of a wheel, the basic technology of pre-industrial ironworking. Spillage from this upper weir fed the Middle Forge Hammer Mill further down the slope, an L-shaped building extended in the 1930s to accommodate a cutlery finishing shop. Large sections of its wooden pitchback waterwheels survive in place, each over four metres in diameter, along with the wooden hammerbeam and cast-iron head of one trip hammer. Below these, the outfall ran on to feed the lower mill pond shared by the Logwood mill and the Coolowen Forge Hammer Mill. The Logwood mill began life crushing woodchip for logwood dye before being converted to spade and shovel production in the mid-nineteenth century; by 1950, a diesel engine had been installed and the old waterwheel repurposed as a flywheel to smooth the transmission of power. The Coolowen mill, built into a rock face on three sides, retains a breastshot waterwheel with thirty elbow buckets, as well as the remains of a manually operated guillotine. Workers' cottages, some eighteenth-century and some still occupied, stand to the east of the middle mill.

The 1842 Ordnance Survey six-inch map shows O'Hara's and the Middle Forge Mill already in place by that date, suggesting the lower pair came later. The whole sequence, water management infrastructure, machinery, ancillary buildings, and domestic housing, survives as an unusually complete record of how a small industrial operation was organised and sustained over generations.