Grjótagjá is a small lava cave near Lake Mývatn that’s best known for its appearance in Game of Thrones. Inside, you’ll find a narrow crack opening into a beautiful blue pool, which makes it a really cool (and quick) photo stop. I would personally only make a stop here if you have extra time, otherwise it's not a must-see.

It used to be a popular hot spring, but geothermal activity has raised the water temperature too much, so bathing is no longer allowed.