The red brick edifice was the engine house that supplied the draught for the furnaces. Judging from aerial photos, this building is now the only surviving relic of the steelworks. The works occupied a steeply sloping site. Cae Harris station and the sidings at Furnace Tops were level with the top of the structure seen here. The lower level parts of the steelworks were reached by the aptly named Zigzag Lines.