During the summer months, from the end of May through mid-September, there are several ranger-guided programs offered at the park. The time and locations of the talks can be found in the park newspaper, which can be picked up at the Pinnacles Entrance and at the Ben Reifel Visitor Center [1]. All of the programs are free.
Programs include a 45-minute Geology Walk at the Doors/Windows trailhead, which is located two miles northeast of the Ben Reifel Visitor Center off of Highway 240.
There is also a 15–20-minute Fossil Talk at the Fossil Exhibit Trail [2], located on Badlands Loop Road [3], about five miles northwest of the Ben Reifel Visitor Center.
A half-mile Prairie Walk features a discussion of the wildlife and plants of the prairie. The walk also begins near the Ben Reifel Visitor Center.
In the evening, plan on attending the very popular 40-minute Night Sky Program, which begins at dark, sometime between 8 and 9 p.m. This program is held at the amphitheater at the Cedar Pass Campground [4], within walking distance of the Ben Reifel Visitor Center.
For children aged 7–12, a daily ranger-led Junior Ranger Program includes a hike, game, or other activity; at its conclusion, participants earn a Junior Ranger badge.
Links:
[1] http://www.moon.com/destinations/mt-rushmore-the-black-hills/the-badlands/badlands-national-park/sights/ben-reifel-visitor-center
[2] http://www.moon.com/destinations/mt-rushmore-the-black-hills/the-badlands/badlands-national-park/outdoor-recreation/hiking
[3] http://www.moon.com/destinations/mt-rushmore-the-black-hills/the-badlands/badlands-national-park/sights/badlands-loop-road
[4] http://www.moon.com/destinations/mt-rushmore-the-black-hills/the-badlands/badlands-national-park/accommodations-and-food