This huge park encompasses 801,163 acres of magnificent contrasts. Basic facilities include visitor centers, post office, National Park Service campgrounds, a trailer park, store-gas stations and a restaurant-gift shop-lodge in the Chisos Mountains Basin. Advance reservations are strongly advised, especially for holidays and spring break. Chisos Mountains Lodge: 432/477-2291. www.nps.gov/bibe/planyourvisit/lodging.htm.

The Chisos Basin is at an elevation of 5,400 feet and trails go higher from there. The basin and higher Chisos offer backpacking, day hiking on numerous trails, wildlife watching, camping, hotels, restaurants and ranger programs. There is a cost for personal ranger-guided tours—available first-come, first-served.

Pet owners take note: It's best to leave your pets at home. Pets are not permitted on any trail, in the back country or on the river. Pets are allowed in developed campgrounds and primitive roadside campgrounds but must be on a leash at all times. Because of wild animals roaming the park, do not leave any pet unattended. Because of extreme heat, do not leave pets locked in cars.

Open daily. Admission charge. A permit, available at park visitor centers, is required for all back-country and primitive camping; plus for river users. The national park is accessible from Marathon via U.S. 385 (70 miles), from Alpine via Texas 118 (108 miles), and from Marfa/Presidio via U.S. 67 and F.M. 170 (156 miles) . www.nps.gov/bibe .