The town of Hluboka nad Vltavou developed during the 14th century since the very renowned king Chales IV, who has made Prague his capital, often stayed there. The town was then established as a privileged place of residence for the Schwarzenberg family, who built one of the many castles, transforming it in the 19th century into the palace style of today: a rather megalomaniac replica of the English Windsor Castle.
Visiting the place is quite interesting and is worth half a day if you're in the southern Bohemian region and you have time to spare. For those with little time to spend in the Czech Republic, I would recommend that you concentrate on Cesky Krumlov, Konopiste or even Karlstejn instead, which are more worthy of a visit in my opinion.