旷古未有: never seen in past history; unprecedented in history
旷古未闻: unheard-of; never heard of in history; unprecedented
奇闻: sth. unheard-of; a thrilling, fantastic story 短语和例子奇闻逸事 a strange news and an extraordinary affair; 他讲的真是千古奇闻。 what he said is really an unheard-of fantastic story