如果您想用英语表达“难忘的经历”，一种可能的表达方式是 "unforgettable experience"。这个短语来源于拉丁语，"unforgettable" 的意思是 "不能忘记的"，"experience" 的意思是 "经历"。下面是一些例句：
That trip to the mountains was an unforgettable experience.
去山上旅行是一次难忘的经历。
Meeting her was an unforgettable experience.
那次遇见她是一次难忘的经历。
Seeing the aurora boreaps was an unforgettable experience.
看北极光是一次难忘的经历。