From Longman Dictionary of Contemporary Englishlandmarkland‧mark /ˈlændmɑːk $ -mɑːrk/ ●○○ noun [countable] 1 RECOGNIZEsomething that is easy to recognize, such as a tall tree or building, and that helps you know where you are One of Belfast’s most famous landmarks, the Grosvenor Hall, has been demolished.2 IMPORTANTone of the most important events, changes, or discoveries that influences someone or something The discovery of penicillin was a landmark in the history of medicine.landmark decision/case/ruling The Supreme Court issued a landmark decision in January 2001.COLLOCATIONSADJECTIVES/NOUN + landmark a famous/well-known landmarkThe Eiffel Tower is probably the most famous landmark in Paris.a historic landmarkRome is crammed with historic landmarks such as the Colosseum.a prominent landmark (=one that is very noticeable)The castle sits on a hill above the town and is a prominent landmark.a familiar landmarkIt was so dark we could not see any familiar landmarks.a local landmarkThis oddly shaped rock is a well-known local landmark.a major/significant landmark (=an important one)From Parliament Hill, you can see most of London's major landmarks.a London/New York/Paris etc landmarkBuckingham Palace is a London Landmark.
Examples from the Corpus
landmark• This new drug is a landmark in the treatment of cancer.• a landmark court victory• The Washington Monument is a popular historical landmark.• Getting my first part in a movie was a major landmark in my life.landmark decision/case/ruling• In a landmark decision, the U. S. Supreme Court disagreed.• Kay said the ruling violates the Fourteenth Amendment, and could affect landmark rulings on reproductive rights.From Longman Business Dictionarylandmarkland‧mark /ˈlændmɑːk-mɑːrk/ adjective [only before a noun] a landmark agreement, decision, settlement etc is one that is very important and influences how other things developThe company won landmark settlements against several competitors from Japan and South Korea. 