一般来说,城堡是巨大的建筑物,需要打下夯实的地基并且使用石头等材料。
If the foundations are not strong enough, the castle could collapse.
如果地基打的不够坚实,城堡就会倒塌的。
The idea of building a castle in the air-with no foundation at all-is, of course, ridiculous.
在空中建城堡,不打地基,当然可笑至极。
That is why this idiom is used to describe ideas that are not realistic, as if they are dreams orfantasies.
这就是为什么这个习语是用来描述那些不切实际的想法,就像梦跟幻觉一样。
So when someone describes a plan or course of action that we believe may be impossible toachieve, we tell him, "You're building castles in the air."
当我们觉得某人描述的计划或者行动方案是不太可能完成的,我们会告诉他“你是在空中盖城堡。”
A similar idiom is "building castles in the sand."
一则类似的谚语是“沙堆上垒城堡”。
We know that, on a beach, sand castles are inevitably and easily destroyed by the tide.
我们都知道,在海滩上,沙堆城堡不可避免地很容易就会被海浪破坏掉。
They are not built to last a long time.
它们不会维持很长时间。
So when we say someone is "building castles in the sand," we mean they are creatingsomething that won't endure very long.
所以说当我们对别人说“沙堆上垒城堡”,我们的意思是他们建成的东西通常是坚持不了多久的。