Due to the volcanism of Methana there are many sites where you may discovery the remains of volcanism, like thermal springs or relatively cold gas exhausts "mofetta". The most famous baths are situated in the capitol town of the Methana peninsula. There you find sulfuric thermal springs and springs with chlorine, salt and radon gas.
Warm steam can be discovered at some tectonic faults on Nisaki island.
In the Thiafi bay you find gas exhausts and salt concentrations and at Kato Mouska / Agios Nikolaos settlement the so called "baths of Pausanias" where big gas concentration can be found. A little pool there offers the opportunity to experience the healing warm waters.