Here Be Dragons - Except Not Really

For the uninitiated, the phrase 'Here be dragons' (immortalised by classical era fanboys as Hic Sunt Dracones in Latin) was believed to be widely used on maps by cartographers to describe dangerous and otherwise unexplored lands. This phrase would typically lie on the outline of ancient sepia maps, warning would-be travelers of the mysterious great blue yonder.

Of course, aside from a rather trivial exception, this seems to be quite inaccurate. Whilst animals have been used in the past to denote dangers of the unknown (an Anglo-Saxon map warns of lions in Africa, Ptolmey's Geographia atlas warned of elephants, hippos and even cannibals!), the only instance where dragons were mentioned by name comes from the Hunt-Lenox Globe (which is actually on display at the New York Public Library).

The Hunt-Lenox Globe (squint eyes to see Latin)

Made in 1506, this copper sphere was one of the first to be made after Columbus' expedition to the New World. Stamped on Southeast Asia , the Latin words 'Hic Sunt Dracones' lie ominously on the model. Recent commentators have downplayed the warning-aspect of the sentence, stating that the words referred to the intimidating Komodo dragons that were known to inhabit islands off the coast. [1] No doubt that stories of their ferociousness were probably the main reason as to why they were included on this map and not for the sake of medieval folklore and mythology.

Scholar Dennis McCarthy summarises the entire misconception well:

"The phrase was not, as so many believe, a general warning to sailors about alien realms. It was, instead, one of the first recorded post-Columbian biographical remarks and has now become, perhaps, the most famous distributional comment ever, likely marking the general region where tales of the Komodo dragon originated"[1]

References:
  1. Dennis McCarthy (2009). Here be Dragons – How the study of animal and plant distributions revolutionized our views of life and Earth. Oxford University Press. ISBN 0-19-954246-5.