The story of a prisoner inside an enormous steel mountain is embedded in Kullervo, an early Finnish tragedy by 19th-century author Aleksis Kivi. I focus here on the exceptional size of the mountain, as told by the main character, Kullervo. Although the embedded story has aroused admiration in research, the mountain’s size and form do not appear to have done so. If taken literally, and assuming the shape of a double pyramid, at a minimum, the mountain’s surface area would be between that of Earth and Uranus, a planet that Kivi was somehow aware of. The mountain’s maximum surface area and volume would greatly exceed that of the Sun. This mountain cannot be localized in the near environment of the characters. A prisoner’s captivity inside the allegorical mountain creates images of anguish, deprivation of freedom, and possibly of punishment and remorse. It could be interpreted symbolically, as reflecting Kullervo’s unbearable shame and wrath toward his own slavery, which are later, expressed toward himself as a murderer and escapee.