Yold Ruins in the fourth and final area of Chapter 1 in the game Super Paper Mario. It is located in Lineland past Yold Desert and is the main setting of Chapter 1-4. It is also home to the second Pure Heart of the game.
Chapter 1-4: Monster of the Ruins
Mario and Tippi finally arrive in Yold Ruins where Tippi senses a Pure Heart nearby. They make their way though the ruins fighting through the many enemies that are there and solving the puzzles. Eventually, Mario and Tippi make it outside where they are soon greeted by Fracktail who has been guarding over the Pure Heart until the hero of the Light Prognosticus appears. After identifying Mario as the hero, Fracktail is about the lead the way to the Pure Heart until one of Count Bleck's henchmen, Dimentio, appears. Dimentio, not wanting to make things easy, sabotages Fracktail into attacking Mario (where this is actually part of Dimentio's plan to test out Mario's power). After an intense battle, Mario defeats Fracktail and Fracktail apologizes for it's malfunction before blowing up wishing Mario will save the world. A door soon appears and Mario and Tippi head into it where they enter what it appears to be a chamber. They are soon greeted by Merlumina who explains the story about the Light and the Dark Prognosticus more. After the story, Merlumina disappears and Mario and Tippi acquire the second Pure Heart.