Two stone structures that were part of an iron smelting operation
The two stone stacks are hard to see from the RR tracks when the leaves are out. They are several stories tall and built against a cliff. A nearby home was once a residence for workers, and the remains of the burnt out store are still visible.
The link to the NRHP nomination below has good pictures and lots of history.
The first 7 pictures are of the old train stop f.n.a. 'Grotto'. It's where passengers would disembark and spend time along the Piney Creek and local area attractions.
Topo map from 1909 here: