a prominent or conspicuous object on land that serves as a guide, especially to ships at sea or to travelers on a road; a distinguishing landscape feature marking a site or location: The post office served as a landmark for locating the street to turn down.
something used to mark the boundary of land.
a building or other place that is of outstanding historical, aesthetic, or cultural importance, often declared as such and given a special status (landmark designation) ordaining its preservation, by some authorizing organization.
a significant or historic event, juncture, achievement, etc.: The court decision stands as a landmark in constitutional law.
to declare (a building, site, etc.) a landmark: a movement to landmark New York's older theaters.