The name conjures smelting and industry, yet the structure itself tells a more puzzling story. Measuring just under five metres in diameter, it has four short rectangular gabled projections extending outward at the cardinal points, a layout that has led at least one expert to suggest it was not an industrial furnace at all, but a gazebo or summer house. The label, it seems, may have drifted onto the wrong building entirely.

The industrial history of this corner of Muckross is well documented, even if the individual structures within it are harder to interpret. Copper mining here took place across at least six distinct phases, beginning around 1749 and running until 1818. The workings were spread across three locations close to the lake shore, and the evidence is still visible on the ground: partly infilled vertical shafts, surface spoil deposits, and the ruins of three stone buildings in the central mine area. One of these is a powder magazine, a small stone store built to hold the explosive charges used to break rock underground, and its connection to mining is beyond doubt. The other two buildings, including the larger one that inherited the "Old Furnace" name on the 1846 and 1895 six-inch maps, have no firmly established function. The label may reflect a local tradition, a cartographer's assumption, or knowledge that has simply not survived.

The site sits in woodland to the north of a pedestrian road, and the mine shafts, though partly infilled, remain open enough to reward careful attention. The spoil heaps and shaft openings cluster along the lake shore, and the ruins of the stone buildings are distributed across the central area of the mine complex.