Suppose you own a garden-variety object such as a hat or a shirt. Your property right then follows the ageold saw according to which possession is nine-tenths of the law. That is, your possession of a shirt constitutes a strong presumption in favor of your ownership of the shirt. In the case of land, however, this is not the case. Here possession is not only not a strong presumption in favor of ownership; it is not even clear what possession is. Possessing a thing like a hat or a shirt is a rather straightforward affair: the person wearing the hat or shirt possesses the shirt or the hat. But what is possession in the case of land? This essay seeks to provide an answer to this question in the form of an ontology of landed property.