premise: The Prague Castle is a location.
hypothesis: Prague Castle ( [ cz : Pražský hrad , Pražský hrad ] ) is a castle complex in Prague , Czech Republic , dating from the 9th century . It is the official residence 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 . According to the Guinness Book of Records , Prague Castle is the largest ancient castle in the world , occupying an area of almost 70000 m2 , at about 570 m in length and an average of about 130 m wide . The castle is among the most visited tourist attractions in Prague attracting over 1.8 million visitors annually .