I've read about a similiar structure in Philadelphia that is meant as a sledding hill where instead of hauling away excess soil they created a hill. There are similar hills along the Pennsylvania Turnpike where excess fill is piled in a mound along the roadway presumably to save the cost of hauling the soil away. Is there a way to tag a man-made hill? Or is embankment the best solution. This site has another "cairn" to the northwest.