Porolissum is the largest and best-preserved archaeological sites in all of Romania.

Porolissum is among the largest and best-preserved archaeological sites in all of Romania. Established in C.E. 106 by the Roman emperor Trajan, Porolissum helped defend the main northwestern passageway through the Carpathian Mountains into the province of Dacia. By the early third century, Porolissum had blossomed into a proper city with standard Roman features such as an amphitheater, temples and a forum. The population stood at 20,000. Due to the tremendous costs involved in maintaining an army in this portion of the Empire and the growing need to shift troops to the East, Aurelian withdrew from Dacia in C.E. 271. The post-Roman period of Porolissum is poorly understood. The city was inhabited steadily through to C.E. 375/425. Following a sharp demographic decline, the city enjoyed another prosperous moment between the sixth and eleventh centuries.