The little secluded town of Therma in Ikaria is the best spot to unwind after a full day of exploration of the island.

As the name suggests, there are underwater hot springs right on that spot, where you can just get in the water and let the hot waters heal you.

That particular spot lies on the right end of the small port, under rocks that look like a cave. If you're there in the summer, you'll probably see people just lying there on the rocks, in the shallow waters. Otherwise, you can try the organized facilities to enjoy the hot healing waters at the municipal spa centre, right there by the beach.
The town of Therma is built mainly around the bay, where you will find a few tavernas with traditional Greek food, seafood, Mediterranean food, as well as cafes and small, family run hotels.
A short drive away is Ayios Kyrikos, Ikaria's main port and town, where the ships come and go towards the port of Piraeus and the islands nearby.