Through andesitic tuffs and cobblestones associated with the intense volcanic activity of Lepetymnos, along tectonic discontinuities, the chlorosodium radioactive hot spring of Eftalou emerges.
The water temperature is 43.6oC to 46.5oC.
It shows a harmless radioactivity of 14.7 Mach and is the most radioactive healing source of Lesvos.
