La Gomera is one of Spain's Canary Islands, located in the Atlantic Ocean off the coast of Africa. In area, it is the second-smallest of the seven main islands of this group. The island is of volcanic origin and roughly circular; it is about 22 km in diameter and rises to 1487 m at the island's highest peak, Garajonay.
The inhabitants of La Gomera have a unique way of communicating across deep ravines by means of an amazing whistled speech called Silbo Gomero. This whistled language is indigenous to the island, and its existence has been documented since Roman times. When this unique means of communication was threatened with extinction at the dawn of the 21st century, the local government required all children to learn it in school. (source)
Thank you Fernando!