This is the Beckley Furnace, a blast furnace built in 1847 and restored by the state. I'd never seen a real blast furnace before. Those of us who have visited the Steel Museum in Youngstown OH know that a blast furnace smelts iron ore and produces pig iron. (Only the first step in making steel.)
This thing was loaded with charcoal, limestone, and ore from the top. The square-looking part down at the bottom is the crucible -- the place where the iron collected and then was released into "molds" stamped into sand on the floor.
The neighboring stream was dammed to provide power to force air into the furnace.
