One of the Nation-States of Wars of Liberty, Bulgaria is a Balkan state geographically above Greece and below Romania.
The Balkan States play a bit different than the rest of Europe, Such as the buttons that advance them in Age aren't in the town center but are in the Barracks, Stable, Artillery Foundry, Hunting Lodge, and Market.
My home city is named "A Sofa in Sofia" as if it's just a random couch (my Explorer is the proud owner of the Sofa).
Serbia's Military units are available one age later than normal and Serbia has access to the Star Fort.