When old cartographers make errors, or indeed completely falsified information, it can take a long time to discover their mistakes. In some cases, islands on maps that never actually existed would continue to appear on maps for centuries.
The following 10 are prime examples of just these islands and, in some cases, they were only removed from maps this decade.
This list is far from exhaustive and is no particular order.
1. Thule was a non-existent island off Scotland
Since antiquity, a small island was thought to exist off the coast of Scotland. It was first reported by the Greek explorer Pytheas in around 330 BC and no-one appears to have checked for centuries.
This is later both supported and questioned by the Roman geographer Strabo. In his 30 AD book "Geographica", he mentions that Thule is "six days" sail North of Britain.
But he does also throw its existence into question when he later stated that Pytheas has often "been found, upon scrutiny, to be an arch falsifier". Strabo was clearly a man who didn't sugarcoat his critiques.
It still appeared on some later maps of the British Isles as late as 1720 AD. According to these maps, the Island of Thule could be located off the North coast of Scotland.
Modern interpretations of ancient Greek and Roman sources regarding Thule include it being either Orkney, Shetland or the Norwegian island of Smøla.
2. Sandy Island was recently "undiscovered"
Sandy Island existed on maps until it was officially removed from them 6 years ago. Before then it even appeared on Google Earth and was located between New Caledonia and Australia.
It first appeared on records as an island in 1876 and was first depicted on British maps in 1908.
From 1974 the island was removed from French hydrographic charts but remained on others for a further 28 years. It wasn't until the R/V Southern Surveyor, an Australian research ship, sailed through the area in 2012 and officially "undiscovered" it.
It has since been removed from most modern maps and data sets including Google Earth.
3. The Nimrod Islands never existed
The Nimrod Islands were first reported in 1828 by Captain Eilbeck. He named the supposed islands after his ship the "Nimrod" and 'found' the islands whilst sailing from Port Jackson around Cape Horn.
Captain Eilbeck indicated that the new islands were east of Emerald Island and west of Dougherty Island. All of these are now considered phantom islands.
Further attempts to confirm the presence of the islands failed, including the 1909 exploration mission by another ship called the "Nimrod". Lars Christensen mounted another attempt to find them in 1930 but reported the area to be nothing but empty sea.
4. Ireland was not the only Emerald Island
The Emerald Island was once thought to lie somewhere between Australia and Antarctica somewhere south of Macquarie Island. It was named after the British ship that first spotted it in 1821, the Emerald.
Reports from the ship's log indicated it was believed to be a small island that was high and mountainous. Further investigations in 1840 by the U.S. Exploring Expedition found no further trace of it.
Another ship reported spotting it in 1890 but this claim was further refutted in 1909 by "The Nimrod" during an exploration mission of the area. Despite these discoveries and "undiscoveries" the island actually appeared on a 1987 desk calendar book published by American Express.
5. Dougherty Island never actually existed
Dougherty Island is another phantom island that was once thought to be located roughly halfway between Cape Horn and New Zealand. It was named after one Captain Dougherty who reported the island's existence in 1841.
According to his description, the island was roughly 5-6 miles long and had a high bluff to its NE. It was also covered in snow.
Amazingly the island's existence was later confirmed twice, by two different ships. The first was in 1860 by "The Louise" and the second by "The Cingalese" in 1886.
Further thorough explorations during the 19th and 20th centuries failed to find it again. The same exploration mission that "undiscovered" the Emerald island also erased Dougherty Island from the map in 1909.
Captain Davies of "The Nimrod" later explained the earlier sightings as possible large icebergs and/or fog banks.
6. Bermeja island either never existed or could have been blown up by the CIA
Bermeja was an islet thought to exist off the North coast of the Yucatan peninsula. It appeared on several maps of the area between the 16th and 20th centuries.
It was first described by Alonso de Santa Cruz in his list of islands of the region in 1539. Its precise location is given in "Espejo de navegantes" by Alonso de Chaves, who wrote that from a distance, the small island looks "blondish or reddish".
In 1844 British maps of the region described the islet as sunk and further attempts to find it in 1997 and 2009 met with failure. For many years there have been various explanations for the apparent disappearance of the Bermeja.
These range from cartographic error (most likely), rising sea levels or subsea subsidence to a conspiracy theory that the island was destroyed by the CIA.
7. Crocker Land was a complete fabrication
Crocker Land was once thought to be a huge island spotted from the top of Cape Colgate in 1906. The claim was made by the polar explorer Robert Peary on his failed attempted to reach the North pole that year.
Peary named his discovery after one of the expedition's financial backers George Crocker. It has since been shown to be a completely fraudulent claim.
The invention of Crocker Land was apparently an attempt to secure further support from Crocker for Peary's 1909 expedition. The gambit ultimately failed and Crocker diverted much of his available resources to rebuilding San Francisco after the devastating 1906 earthquake.
8. Frisland was long assumed to exist
Frisland, Frischlant, Friesland, Frislanda, Frislandia, or Fixland is another phantom island that never actually existed. It appeared on practically all European maps of the North Atlantic between 1560 and the 1660s.
It's origins appear to stem from cartographic errors that may have confused it with the southern tip of Greenland or an approximation of Iceland. Whatever the case, by 1558 it started to appear as a completely independent land mass, most notably on the influential Zeno Map.
This land mass was depicted south or south-west of Iceland and continued to be plotted on maps for the next 100 years. It would appear on and off maps after the 1660s.
It was finally erased from maps as explorers from England France began to navigate and chart the region in more detail over the centuries.
9. The Spanish used to think California was an island
Believe it or not but California was depicted as an island for centuries on maps. Today, we know this is not the case and its surprising it took so long to correct.
The myth that California was an island dates back to errors made by Spanish mapmakers in the 16th Century. This is one of the most famous cartographic errors in history and one that would go unchanged for 100's of years.
It wasn't the 18th Century that the Californian peninsula was finally officially recognized as a peninsula and not an island. This followed various contradictory reports from explorers of the time and was finally settled when King Ferdinand of Spain finally declared that "California is not an island" in 1747.
10. Saint Brendan’s Island
Saint Brendan's Island is another phantom island that has since been shown to have never existed. It was supposed to have been situated in the North Atlantic somewhere west of Northern Africa.
The island was named after one Saint Brendan of Clonfert who was said to have discovered the island whilst evangelizing in the area. This mythical island appeared on various maps during the 15th Century.
The first reference to the island appears in the 9th Century in a Latin text called Navigatio Sancti Brendani Abbatis ("Voyage of Saint Brendan the Abbot"). This cemented the island in Irish and European folklore.
It's most famous depiction is on a map created by Martin Behaim, Erdapfel, that was plotted in 1492. It has since been proven to be a myth.