Originally a prince´s fortress in the late ninth century, Prague Castle was begun by Prince Bořivoj of the Přemysl family.
At the turn og the eleventh century it was used as a roman basilica. Extensive repairs and projects were undertaken during the reign of Charles IV, such as beginning construction of St. vitus Cathedral, during which time the castle served as the emperor´s residence.
Later, under the direction of Vladislav Jagellonský, gothic architecture began to appear. At the beginning of the sixteenth century under the direction of the Hapsburgs, the castle was remodeled according to Renaissance desing (The Royal Gardens Summer Home).
Extensive remodeling was initiated during the reign of Rudolf II, at which time the castle became the Center for Arts and Sciences. During the seventeenth century, Prague castle was only occasionally used as the emperor´s governmental seat, which had been previously moved to Vienna.
Additional construction and repairs were postponed until the eighteenth century during the reign of Mary Terezie, during which time it was remodeled yet again in the classic rococo style.
In 1918, Prague castle became the seat for the governing body of the Czechoslovak Republic led by T. G. Masaryk and from January 1, 1993 to present it has served as the seat for the President of the Czech Republic.

INFORMATION: http://www.zamky-hrady.cz