Alba Iulia (Latin: "Apulum", German: "Karlsburg"/"Weißenburg", Hungarian: "Gyulafehérvár", former ) is a city in Alba County, Transylvania, Romania. It has a population of 66,369 people. It is found on the Mureş River. In the center of the city there is Alba Carolina citadel built in three historical periods: Roman, Medieval and Habsburg.