名词 dream 后面可以接 where 引导的定语从句，此时的 where 相当于 in which。如：

He had a dream where / in which a lion was chasing him in the forest. 他做了一个梦，梦见在森林里有一只狮子追他。

名词 dream 后面可也以接 that 引导的同位语从句。如比如上面一句也可说成：

He had a dream that a lion was chasing him in the forest.

更多例句如：

Paulhad a dream that he won the lottery. 保罗梦见自己彩票中了奖。

I’ve had a dream that they’re going to kill you. 我梦见他们准备杀害你。

I had a dream that I was in an old study, surrounded by leather books. 我梦见我在一间古老的书房里，四周全是皮装书。

也就是说，网友的句子填 where 或 that 均可：填 where 是把 dream 当作一个抽象的地点看待，此时的 where=in which，引导定语从句；若填 that，则引导同位语从句，表示 dream 的具体内容。