The walls of the Prague Castle encompass a whopping 70,000 square meters (750,000 square feet) within their embrace, making this the largest ancient castle in the world. Shaped over 13 centuries, the origins of the castle go back to 870 CE when the Church of the Virgin Mary was built. Former residence of the kings of Bohemia, Roman Emperors and the Presidents of Czechoslovakia, the regal abode is rife with historic treasures, man-made marvels and artistic triumphs. A mélange of architectural styles that spans the ages, the castle is an inspiring sight to behold; a monumental, visual chronicle of the march of time and the prevalent trends of each era. Of special interest is the St. Vitus Cathedral boasting vibrant stained glass windows and the tomb of St. John of Nepomuk.