Prague Castle
The Prague Castle, an ancient symbol of the Czech lands, is the most significant Czech monument and one of the most important cultural institutions in the Czech Republic.
The Prague Castle was most likely founded in around 880 by Prince Bořivoj of the Premyslid Dynasty (Přemyslovci). According to the Guinness Book of World Records, the Prague Castle is the largest coherent castle complex in the world, with an area of almost 70,000 m². A UNESCO World Heritage site, it consists of a large-scale composition of palaces and ecclesiastical buildings of various architectural styles, from Roman-style buildings from the 10th century through Gothic modifications in the 14th century. The famous Slovenian architect Josip Plečnik was responsible for extensive renovations in the time of the First Republic (1918-1938). Since the Velvet Revolution, the Prague Castle has undergone significant and ongoing repairs and reconstructions.
More info: http://www.hrad.cz/en/prague-castle/prague-castle-tourist-information/visit-of-prague-castle.shtml