The Saddle Pass Trail is a 3/10 of a mile long and is accessible from the Park Loop Road, about three miles west of the Ben Reifel Visitor Center. The trailhead is difficult to find, you will have to look for the brown metal posts with small orange marker sticking up out of the ground. When you reach that one scan carefully for the next up the trail. The Saddle Pass Trail is probably one of the most brutal 3/10 of a mile "improved trails" in the National Park Service. It is very steep, and the soil from the butte is loose and the trail is rock covered. Expect for every four steps forward to go one back. Do not attempt this trail in sneakers or open toe footwear. The trail is actually traveled by a lot of people, who are tempted by the seemingly easy 200 foot vertical ascent. However this trail is anything but easy. The reward to the hiker is a spectacular view from the top of the buttes to the south. If you do climb to the top, you will appreciate your altitude by finding your car in the parking lot below.
If you are looking for a challenging and diverse hike, OutdoorPlaces.Com suggests parking your car at the base of the Saddle Pass Trail. Make the climb to the intersection of the Castle Trail and the trailhead to Medicine Root. Take the Medicine Root Trail east to it's end. There you can decide if you are too tired to return via the Castle Trail back to Saddle Pass. This entire loop is about 5.2 miles and will take close to three hours. Make sure to bring at least one gallon of water for each person if you are hiking in the late spring, summer or early fall. You should also keep an eye on the sky and bring rain gear as Badlands National Park is famous for it's severe thunderstorms. If you are not tired, you can continue east on the Castle Trail to it's trailhead where you can explore the Door Trail, the Window Trail and the Notch Trail. If you did it all, plus returned on the Castle Trail, you can plan to hike close to nine miles (including all of the doubling back) and should plan for about five hours. Be mindful that on this entire route, there is no potable water. Further, no amount of filtering or boiling will make the Badlands water drinkable.
If you want a real adventure you can hike in the Stronghold Unit located in the southwestern part of the park. This 122,000 acre unit, which was granted to the park in an agreement with the Ogallala Sioux Indians of the Pine Ridge Indian Reservation, was used as an US Army Air Corps bombing range during World War II. There are plenty of unexploded munitions in this area. The White River Visitor Center, the other ranger station in the park has an eight minute video on hiking in this unit. You should make a point to watch this video. Orange markers and yellow flags on the open range should be avoided, as these indicate potential ordinance underground.
If you do hike in the Stronghold Unit be aware that the roads are unimproved and can be made impassible even for a four-wheel drive when it rains. Some of this area is free range for cattle grazing and you will need to respect range etiquette for fences and gates. If you find a gate open, you should leave it open, if you find a gate closed, you should leave it close, and never cut a fence. If you plan to cross private land, it is required by the state of South Dakota to seek permission first.
Camping, Lodging and Touring Badlands National Park...