Journey to the edges of earth in Ethiopia's Danakil Depression
With its technicolor hot springs and lava lakes, the terrain of Ethiopia’s record-breaking-hot Danakil Depression is so bizarre and extreme, astrobiologists study it for insights into life on other planets. The climax of a visit there is a trek up to the rim of an active volcano, where you can peek into the fiery underworld beneath the Earth’s crust. Guests of Wild Frontiers camp near the edge of the crater (at a safe distance, of course). 10 nights, from $4,440.