Be warned, it’s addictive – at Bros Thermá Hot Springs several hours can pass by before you even notice. Kos’ volcanic heart pumps out a steady stream of scalding water into a shore-edge pool formed by enormous boulders, where it mixes with the Aegean to cool to comfortable temperatures. The pool’s shape – though not its depth, a maximum of 4 feet – changes annually, as the Bros Thermá rocks are tumbled about by winter storms and have to be rearranged every April. Bring everything you need as the little drinks-and-ice-cream canteen operates fitfully at best out of adjacent changing rooms. In theory, Bros Thermá is set to be developed as a regimented spa with an admission fee, so enjoy it au naturel while you still can.