Grjótagjá

Game of Thrones fans may recognise this as the place where Jon Snow is, ahem, deflowered by Ygritte. Grjótagjá is a gaping fissure with a 45°C water-filled cave. It's on private property – it's prohibited to bathe here, but the owners allow the public to visit and photograph. This is a beautiful spot, particularly when the sun filters through the cracks in the roof and illuminates the interior. There is easy road access.