White Sands takes up 275 square miles of breathtaking landscape in New Mexico. Its most noticeable feature: miles of undulating dunes made of blindingly white gypsum crystals which were formed 10,000 years when shallow sea that had existed for millions of years dried up, leaving the gypsum behind. Though long a National Monument, White Sands was elevated to park status in December 2019. Four marked trails allow hiking, and since gypsum, unlike sand, reflects the sun’s heat, the dunes are easy on your feet. And if you’re so inclined, you can rent plastic sleds to slide down them.