The snail hill is a palaeonthological reservation, geologically unique, 65-70 million years old, and it represents an alternation of grit stone and marl conglomerates with 35 species of mollusk. You can actually see the snail fossils in the rock!
To visit this, you can check in to a beautiful pension: Pensiunea Craiul.
Transylvania is in the Northeast corner of Louisiana, not far from the Arkansas border. I drove a little out of the way just to see it because of the name. There is very little here except a souvenir shop/gas station/cafe where you can buy all your gift needs. They, of course, trade heavily on the name and the legends of the other Transylvania (like Dracula).