The McIntosh Sugar Works was a sugar mill built in the early 1800's. It is located near the Kings Bay Naval Base in St. Mary's, GA. This was a site we came across when we camped at the Crooked River State Park in 2008. I've posted a link to my YouTube site with some photos of this hidden ruin.
The walls are constructed of a kind of primitive concrete mixed with broken shells, which would have been abundant this close to the seashore. You can still make out where beams would have been located in the walls to support the floor and walls. If you are in the area of Southern Georgia, this is a neat place to stop and check out. It is on the National Register of Historic Places.