1 Best Sight in Organ Pipe Cactus National Monument, Southern Arizona

This designated part of the Sonoran Desert preserves more than two dozen species of cacti, including the park's namesake, as well as other desert plants and animals. Because organ pipe cactus tend to grow on the warmer, usually south-facing slopes, you'll get the best views by taking either the 21-mile scenic loop Ajo Mountain Drive (a one-way, partly dirt road) or Puerto Blanco Drive, a 45-mile loop road (4-wheel drive vehicles are recommended). Ranger-led talks and guided van tours are offered January through April. Check with rangers for the schedule of "trailhead drops," which enable hikers to leave their cars in more populated areas.