The term 'Capital on the Danube' refers to four cities located along the Danube River in Central and Eastern Europe. Bratislava (10 letters) is the capital of Slovakia, VIENNA (6 letters) is the capital of Austria, BUDAPEST (8 letters) is the capital of Hungary, and Bratisl (7 letters) is an alternate spelling of Bratislava. All four cities are major cultural, economic, and political centers in their respective countries.