Why not spend your time in a hotspring as you wait for your flight!
There are actually several sources in this little bay near the airport. First of all there is a completely natural inlet where hot water pours from the seabed gravel beneath. It’s on the left if you arrive to abandoned spa in the end of the road and beyond the concrete platform. You can see in the bottom right corner in the photo above.
[update 2024: the concete pool next to the platform holds thermal water!]
Then there is a designated bathing place with a man made concrete pool and a changing cabin. Find it following the path to the right from the abandoned spa. Although we found that the latter being spoiled by massive amounts of plastics in it’s surrounding beach. We could also detect smaller sources of hot water along the shore, but not enough to make a bath.
As with any spring in Ikaria: 20min should be the maximum time you spend due to radon 222 content of the water. Literature says Agia Kyriaki spring is 40,3°C and 54ME.
Agia Kyriaki, Ikaria, Greece: If you are not turned down by the polluted surrounding, very pleasant dipping especially with calm sea! – bert