A visit to the museum is an unforgettable experience.

对该博物馆的参观是一次难忘的经历。

It was an unforgettable experience.

这是一次难忘的经历。

It's unforgettable experience for me.

对我来说是难忘的经历。

Your unforgettable experience of camping.

你难忘的露营经验。

That trip was an unforgettable experience.

那次旅行是一次难忘的经历。