The Oxford Thesaurus An A-Z Dictionary of Synonyms - landmarkn.

1) feature, guide, guidepost; identification: The tower serves as a landmark for those seeking the castle. 2) turning-point, watershed, milestone, monument: His essay remains a landmark in philosophical thought. --attributive 3 critical, crucial, pivotal, important, historic, significant, precedent-setting, momentous, notable, noteworthy, major: This stands out as a landmark decision in the annals of criminal law.