"The Ion Adventure Hotel is located near a tectonic boundary simmering with geothermal energy, and summer weather softens the lava fields of Nesjavellir with new growth that hints at energy beneath the surface. Icelandic wool blankets and amenities made with local herbs are some of the hotel’s many sustainable touches, which make this an eco-friendly home base for exploring Thingvellir National Park. There, you can take advantage of the mild summer temperatures to snorkel the Silfra Rift between the North American and Eurasian plates, or take a shaggy Icelandic horse for a cross-country ride under late-night sunshine. 64˚ north; +354 482-3415; doubles from about $440 per night." - Jen Rose Smith