This 30-mile route at Big Bend National Park, Texas is for at least mid-level hikers. It’s strenuous and there are significant elevation changes and primitive trail. The time to try it out is between October and May; it gets too hot in the summer. The loop is Big Bend's signature multi-day backpacking trip and includes a wide variety of habitats and scenery including, the piñon/juniper/oak woodlands of the Chisos, and stark, rugged desert in one of the most wild and remote corners of the country, according to NPS.