The last surviving example of a Sheffield cementation furnace, the iconic conical brick chimney that once dominated the city's industrial skyline. There were over 250 of these furnaces in 19th-century Sheffield, all used to harden wrought iron into blister steel by sealing it with charcoal and firing for a week. This one in Doncaster Street was built around 1848 and remained in use into the early 20th century.
The site is open and free to view from outside at any time; small interpretive plaques explain how the furnace worked. The Kelham Island Museum five minutes' walk away gives the full industrial context.