The Golden Gate Bridge is a famous/familiar 'landmark' in San Francisco.
The moon landing is a 'landmark' in space exploration.
The decision/ruling was a 'landmark' in legal history.
(..) GIRL: Come on. SOLICITOR: Save the clock tower! Throw in $ and help save the clock tower. Sorry, no. - That's an important historical landmark! - Some other time. SOLICITOR: Lightning struck that thing years ago. MARTY: Wait a minute. Cubs win World Series... (..)1989 Back to the Future Part II