land·mark: studio practice as a series of landmark to track down the change

 [ˈlændˌmɑrk]

noun

1.

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.

2.

something used to mark the boundary of land.

3.

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.

4.

a significant or historic event, juncture, achievement, etc.: The court decision stands as a landmark in constitutional law.

verb (used with object)

5.

to declare (a building, site, etc.) a landmark: a movement to landmark New York's older theaters.