The most historic way to see the park is from the back of a horse the way Teddy Roosevelt did. There are more than 80 miles of trails to explore in the South Unit alone, including the petrified forest (where prehistoric palms, cypress and redwood turned to stone), Halliday Wells and Painted Canyon. Peaceful Valley Ranch offers horse rentals and guided trail rides with lessons and interpretive talks along the way. Riders must be 7 years old and 54 inches tall. You can also reserve rides with Medora Riding Stables.