<http://schema.org/primaryImageOfPage>
"http://media.mnn.com/assets/images/2014/01/great_wall_of_china.jpg"^^<http://www.w3.org/2001/XMLSchema#string>
<http://www.mnn.com/lifestyle/eco-tourism/photos/10-ancient-walls-you-should-see-for-yourself/great-wall-of-china>