Castle Oblivion is a significant location in the Kingdom Hearts video game series. It serves as a mysterious and ever-changing fortress where memories are manipulated and lost. The castle is primarily featured in Kingdom Hearts: Chain of Memories, where characters navigate its halls to confront their pasts. The architecture of Castle Oblivion is unique, with white walls and a surreal atmosphere. Each floor of the castle represents different memories and experiences of the characters, particularly Sora and Riku. As they progress, they face challenges that test their resolve and understanding of friendship and identity.