Old Castle, Formally called Seascape Castle, is a grand six story castle on Pence island, way out in the Soda Sea.
This location was visited in Densetsu no Stafy 3 where our hero, Starfy confronted Ogura and the diabolical being, Evil in a duel in the Castle's Tallest Tower. With help from Starfy's Friends and Ogura, Evil was defeated and Seascape Castle collapsed. Eventually, a Pufftopian contractor and his team journeyed out to Pence island, and set about reconstructing Seascape Castle.
Now, the castle serves as an Amiy outpost Castle in alignment with the Amiy kingdom to this very day.