Description & Facts: Rijeka is the principal seaport of Croatia, located on Kvarner Bay, an inlet of the Adriatic Sea. It is Croatia's third largest city. Created a free port in 1723, Fiume was passed during the 18th and 19th centuries among the Habsburgs' Austrian, Croatian, and Hungarian possessions until its attachment to the latter kingdom for the third and last time in 1870. Although Croatia had a constitutional autonomy within Hungary, the City of Fiume was independent, governed directly from Budapest by an appointed governor, as Hungary's only international port.