Zanzibar?
An island situated in front of Monte Argentario, in the Tyrrhenian Sea between the Isola del Giglio and Giannutri. It was reported for the first time by the cartographer and astronomer Gerardus Mercator in 1589 and subsequently reported in numerous ancient maps by illustrious cartographers until 1720.
Approx. 83°W, 32°S (northwest of Robinson Crusoe Island), noted as “Existence doubtful” in Operational Navigation Chart of the United States Department of Defense.
A nonexistent reef in the Line Islands (in fact Line Islands are more than 2,000 miles (3,200 kilometres) away) along with Ernest Legouve Reef, Jupiter Reef, and Maria Theresa Reef. This reef, the largest of the three, was thought to be 30–35 feet (9.1–10.7 metres) deep. None of these reefs are currently believed to have actually existed.
A vanished group of islets in the Cook Islands at which a sailor allegedly spent 6 days, but a ship traveling in the waters two years later found no island.
A possible reef in Southern Palau. While this reef probably exists, some maps do not list it as an actual location, and, although the reef doesn’t have any land, the native name of the island, Pieraurou, means ‘Sandy Navigation Point’, implying a sandy island or sand bar.
A mythical island near Ambon in the East Indies purportedly destroyed by a volcanic eruption.
A mythical island in the far north that is mentioned many times in Roman- and Medieval-period works. Current interpretations guess it to be Norway, Orkney, Shetland, Scandinavia, Iceland, Greenland, and even Saaremaa.
An island in the south Atlantic Ocean discovered by the whaling ship captain George Norris; it has not been seen since 1893.
Thought to lie off Oates Coast, East Antarctica.