a prominent or conspicuous object on land that serves as a guide, esp. 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.

noun

battleground , benchmark , bend , blaze , feature , fragment , guide , hill , mark , marker , memorial , milepost , milestone , monument , mountain , museum , promontory , remnant , ruins , souvenir , specimen , stone , survival , trace , tree , vantage point , vestige , waypost , crisis , event , stage , watershed , achievement , cornerstone , guidepost , signpost