Prague Castle Picture Gallery. Prague Castle is a castle complex in Prague, Czech Republic, built in the 9th century. It is the official office of the President of the Czech Republic. The castle was a seat of power for kings of Bohemia, Holy Roman emperors, and presidents of Czechoslovakia. The Bohemian Crown Jewels are kept within a hidden room inside it. According to the Guinness Book of Records, Prague Castle is the largest ancient castle in the world, occupying an area of almost 70,000 square metres, at about 570 metres in length and an average of about 130 metres wide. The castle is among the most visited tourist attractions in Prague attracting over 1.8 million visitors annually. The history of the castle began in 870 when its first walled building, the Church of the Virgin Mary, was built. The Basilica of Saint George and the Basilica of St. Vitus were founded under the reign of Vratislaus I, Duke of Bohemia and his son St. Wenceslas in the first half of the 10th century. The first convent in Bohemia was founded in the castle, next to the church of St. George. A Romanesque palace was erected here during the 12th century. King Ottokar II of Bohemia improved fortifications and rebuilt the royal palace for the purposes of representation and housing. In the 14th century, under the reign of Charles IV the royal palace was rebuilt in Gothic style and the castle fortifications were strengthened. In place of rotunda and basilica of St. Vitus began building of a vast Gothic church, that were completed almost six centuries later. During the Hussite Wars and the following decades, the castle was not inhabited. In 1485, King Ladislaus II Jagello began to rebuild the castle. The massive Vladislav Hall was added to the Royal Palace. New defence towers were also built on the north side of the castle. A large fire in 1541 destroyed large parts of the castle. Under the Habsburgs, some new buildings in Renaissance style were added. Ferdinand I built the Belvedere as a summer palace for his wife Anne. Rudolph II used Prague Castle as his main residence. He founded the northern wing of the palace, with the Spanish Hall, where his precious art collections were exhibited. The Third Defenestration of Prague in 1618 took place at the castle and began the Bohemian Revolt. During the subsequent wars, the Castle was damaged and dilapidated. Many works from the collection of Rudolph II were looted by Swedes in 1648, in the Battle of Prague which was the final act of the Thirty Years' War. The last major rebuilding of the castle was carried out by Empress Maria Theresa in the second half of the 18th century. Following his abdication in 1848, and the succession of his nephew, Franz Joseph, to the throne, the former emperor, Ferdinand I, made Prague Castle his home. In 1918, the castle became the seat of the president of the new Czechoslovak Republic, T.G. Masaryk. In this period the St Vitus Cathedral was finished. On March 15, 1939, shortly after the Nazi Germany forced Czech President Emil Hacha to hand his nation over to the Germans, Adolf Hitler spent a night in the Prague Castle, proudly surveying his new possession. During the Nazi occupation of Czechoslovakia in World War II, Prague Castle became the headquarters of Reinhard Heydrich, the Reich Protector of Bohemia and Moravia. According to a popular rumor, he is said to have placed the Bohemian crown on his head; old legends say a usurper who places the crown on his head is doomed to die within a year. Less than a year after assuming power, on May 27, 1942, Heydrich was ambushed during Operation Anthropoid, by British-trained Slovak and Czech resistance soldiers while on his way to the Castle, and died of his wounds-which became infected-a week later. Klaus, his firstborn son, died the next year in a traffic accident, also in line with the legend. After the liberation of Czechoslovakia and the coup in 1948, the Castle housed the offices of the communist Czechoslovak government. After Czechoslovakia split in 1993 into the Czech Republic and Slovakia, the castle became the seat of the Head of State of the new Czech Republic. The castle buildings represent virtually every architectural style of the last millennium.