It was a big district in Central Europe of the Roman Empire. The northern part of the border was made up of the Carpathians; the southern part of the border of Dacia was made up of the Danube River, and the western part of the border of Dacia was made up of the Tisza River. Along the borders many Roman strongpoints built. The Dacia district protected the Empire from foreign tribes of the north east side.
The place where Dacia once was is now made up of Romania and Moldova, along with some parts of Hungary, Bulgaria and Ukraine. The capital of Dacia was Sarmizegetusa. The name of Romania came probably from the idea of the former "Romans country".
Media related to Dacia at Wikimedia Commons