Grjótagjá is a small lava cave near Lake Mývatn in north Iceland, known for its stunning geothermal hot spring. Once used as a bathing spot, it gained fame as a filming location for a steamy scene in Game of Thrones. While you can't take a dip anymore due to unpredictable geothermal activity, the cave's eerie beauty still attracts visitors looking for a taste of Westeros in real life.