Scalding water between pebbles on the beach!
Described as a geothermal field Megala Therma is pretty exceptional. There is daily earthquakes stemming from this region which is part of a Skyros-Edremit Fault zone between Lesvos and Turkey. And there is 70°C hot water at the beach ready to burn your fingers and/or steam your buns.
I spent at least an hour building a pool from the abundant pebbles hoping it would stop the dilution of hot water that occurs with every wave from the sea. I had success and had a dip, but today my hamstrings hurt from all the forward bending while picking rocks.
Megala Therma, Lesbos, Greece: Come and build your own pool! Burn your fingers! It's good fun! – bert