What present-day country was Roman Dacia located in?

Roman Dacia (also Dacia Traiana "Trajan Dacia" or Dacia Felix "Happy Dacia") was a province of the Roman Empire from 106 to 274–275 AD. Its territory consisted of eastern and south-eastern Transylvania, the Banat and Oltenia (regions of modern Romania). The conquest of Dacia was completed by Emperor Trajan (98–117) after two major campaigns against Decebalus' Dacian kingdom.

Dacian royal treasury was of enormous value: 500,000 pounds of gold and 1,000,000 pounds of silver.

With the annexation of Decebalus' kingdom, Dacia was turned into Rome's newest province, only the second such acquisition since the death of Augustus nearly a century before.

Ancient sources implied that Dacia was virtually lost during the reign of Gallienus (253–268), but they also report that it was Aurelian (270–275) who relinquished Dacia Traiana.