Alba Iulia is a city in the Transylvania region of Romania. With a rich history going back to Roman times, it's most known for the Alba Carolina Fortress, a star-shaped fortress filled with Roman Catholic churches and museums. Don't miss the Union Hall, the place where the act of unification of Transylvania with Romania was signed in 1918. And just nearby, lies the fascinating Batthyaneum Library, built in an old baroque church.