Related: There is a whistling language used by people who communicate long distances over a wide river valley. Can be heard at distances up to 5km! https://en.

Related: There is a whistling language used by people who communicate long distances over a wide river valley. Can be heard at distances up to 5km! https://en.wikipedia.org/wiki/Silbo_Gomero https://en.wikipedia.org/wiki/Silbo_Gomero