Mysterious things have been appearing on world maps ever since we started making maps. Because our maps were consistently updated with input from explorers and cartographers, it wasn’t uncommon for an unknown piece of land to show up on them.
While it’s an error most of the times, on occasion, maps do contain things we had no idea existed. Take the Sandy Island in the Pacific Ocean, which showed up on some maps but not others. In reality, there’s nothing there and has since been removed by Google Maps. It’s not entirely an error, though, as the island has been showing up on maps since at least 1876. It was first recorded by a whaling ship called Velocity, and we still have no idea what it is they saw there.
Some say that it must have been a raft, though others believe that it’s a magical island that only shows itself to the worthy.