Inside the cathedral, we find the tombs of Frederick III, Holy Roman Emperor, under whose reign the Diocese of Vienna was canonically erected on 18 January 1469, in the Apostles' Choir (southeast corner of the cathedral). The construction of the Kaiser's tomb spanned over 45 years, starting 25 years before the emperor's death. This impressive sarcophagus is made of the unusually dense red marble-like stone found at the Adnet quarry. Carved by Niclaes Gerhaert van Leyden, the tomb lid shows Emperor Frederick in his coronation regalia surrounded by the coats of arms of all of his dominions. The body of the tomb has 240 statues and is a glory of medieval sculptural art.