Prague Castle (Czech: Praský hrad) and the upper portion of St. Vitus cathedral are outlined against the sky. Prague Castle sits above the city of Prague. It is where the Czech kings, Holy Roman Emperors and presidents of Czechoslovakia and the Czech Republic have had their offices. Prague Castle is one of the biggest castles in the world at about 570 meters in length and an average of about 130 meters wide. The history of the castle stretches back to the 9th century (870) and it has been under construction in one form or another since then.