ION Adventure Hotel

Sitting on the edge of Þingvellir National Park in a sprawl of lava fields and lichen, this adventure hotel is heated geothermically by water pulled from underground at 190°C, so the showers are not in danger of going cold. Rooms are monochrome concrete and reclaimed driftwood, the outdoor hot tub has panoramic views of the otherworldly surroundings, and the activities range from horseback riding to diving between two tectonic plates.