Acadia National Park has 45 miles of carriage roads built in the early half of the 1900s by the Rockefeller family. (Well you know, they paid for it.)
The Rockefellers wanted to create a car-free way to enjoy Mount Desert Island. Today, these dirt and gravel packed paths are used for biking, running and walking (though as the name implies, horses were once more prominent). The carriage roads sounded a lot like to me like the bridle path in Central Park, and for some reason, I assumed they would be largely without incline.