The Grand Canyon, listed as UNESCO World Heritage Site, is the gem of Arizona. Carved by the Colorado River, this amazing rock formation reveals nearly 2 billion years of Earth's geologic history. To admire the sunset, head for the South Rim of the Grand Canyon, the part of the canyon most popular with tourists. To really get your adrenaline pumping, head for the Grand Canyon Skywalk, a transparent horseshoe-shaped ledge located at the dizzying height of 1,200m.