Diner is located somewhere in Oakwood, Georgia.
Throughout The Vampire Diaies Series
In Detoured On Some Random Backwoods Path to Hell Seline took the twins here. They were later joined by Damon and Sybil. Sybil told Damon that Seline is planning on offering them to Cade. They had to run because the people in the diner realized that those kids are kidnapped. Seline used her siren powers to calm them down and escaped before Carline and Alaric could get there.