These are charcoal kilns. They were built by the Pioneer Charcoal Company in the 1950s to process blackjack oak that grew abundantly around the former town of Romeo between Williston and Dunnellon. The raw dark wood from the trees was stacked inside the kilns and slow cooked until it carbonized. It was then compressed and sold as briquettes or lump charcoal.
The smoke from the kilns was so thick at times that it obscured the highway in front of the plant. The kilns haven't been used since the 1960s when the plant was sold and a modern charcoal cleansing facility was built at the site. Boy I'd love to have one of those kilns I sure could cook up something wonderful in clay in one of those.
Here's another stacked tower, a bird tower, with a bird on a handle. It's about twelve inches tall.
I'm leaving the building marks purposefully visible on these. I even left a small hold in the side where the clay was a little short. Thanks for reading and for all your comments.