Fire ant nest
This is about the scariest thing I've got a photo of, hence I'm using it for a Halloween upload. In the last couple of decades, fire ants have become established in Pickens County. (They didn't used to be here.) They are well named -- there are a lot of them in the typical colony, and you can get a lot of bites in a hurry, if you accidentally step on a colony.
This anthill was about a decimeter/3 in tall. However, the Wikipedia article on the Red imported fire ant says that the queen or queens may live as much as a yard/meter under the surface, and that the ants may have tunnels all the way down to the water table.
For a photo of a queen ant, getting ready to swarm, see here.