One of Greece’s best hidden secrets has been given centrestage on the BBC Travel website, which posted a feature on Antia, a tiny village in Evia, perched on Mount Ochi. Antia’s residents have been using a whistled language, not unlike the sound of birds, to communicate across distant valleys. The website found that only six people are left who can ‘speak’ that language in the village, expressing fears that the language, which has been used for 2,500 years, is facing the danger of extinction.

Antia’s residents have been keeping the sfyria tradition tightly guarded, passing it from one generation to the next. According to linguists, the language is effectively a whistled version of spoken Greek, in which letters and syllables correspond to specific tones and frequencies.

Because whistled sound waves are different from speech, messages in sfyria can travel up to four kilometres across open valleys, or roughly 10 times further than shouting. This has enabled farmers and shepherds to conduct entire conversations, often complex ones, with nothing more than whistling. But in the last few decades, the tiny village’s population has dwindled from 250 to 37, and as older whistlers lose their teeth, many can no longer sound sfyria’s sharp notes. This unspoken language, which is not only the oldest, is also the most structured among the 70 recorded whistled languages in the world, all existing in remote mountain villages like Antia.

It is also the one with the fewest living users, which makes it the most critically endangered, according to the Unesco Atlas of the World’s Languages in Danger.

A quest to resuscitate the dying language resulted in the establishment of the Cultural Organisation of Antia in 2010, which has tried to educate younger people in using the language and invited linguists from Harvard and Yale universities to record the whistlers’ notes for future generations.