On one Canary Island, people communicate across valleys by whistling Spanish

Silbo Gomero is a whistled register of Spanish used on La Gomera, developed so herders and villagers could send messages across the island's steep ravines and gorges, audible over several kilometres. It replaces vowels and consonants with distinct whistled tones, and has been taught in local schools since 1999.

— UNESCO Intangible Cultural Heritage listing, Silbo Gomero — Inscribed 2009