Landmark

n.	1.	A mark to designate the boundary of land; any mark or fixed object (as a marked tree, a stone, a ditch, or a heap of stones) by which the limits of a farm, a town, or other portion of territory may be known and preserved.
	2.	Any conspicuous object on land that serves as a guide; some prominent object, as a hill or steeple.
	3.	A structure that has special significance, such as a building with historical associations;
	4.	An event or accomplishment of great significance; as, Brown v. Board of Education was a landmark of the civil rights movement. Also used attributively, as a landmark court decision. Landmarks of history important events by which eras or conditions are determined.

Noun	1.	landmark - the position of a prominent or well-known object in a particular landscape; "the church steeple provided a convenient landmark"
	2.	landmark - an event marking a unique or important historical change of course or one on which important developments depend; "the agreement was a watershed in the history of both nations" Synonyms: turning point, watershed
	3.	landmark - a mark showing the boundary of a piece of land
	4.	landmark - an anatomical structure used as a point of origin in locating other anatomical structures (as in surgery) or as point from which measurements can be taken

bench mark, bookmark, cairn, cardinal point, catstone, chief thing, climax, core, cornerstone, crisis, critical, critical point, crucial, crux, essence, essential, essential matter, feature, fundamental, gist, gravamen, great point, guide, guidepost, heart, high point, historic, identification, important, important thing, issue, kernel, lighthouse, lightship, main point, main thing, major, mark, marker, material point, meat, menhir, milepost, milestone, momentous, notable, noteworthy, nub, pharos, pith, pivot, pivotal, platform, real issue, salient point, seamark, significant, sine qua non, substance, substantive point, the bottom line, the point, tower, turning point, watchtower, watershed