To Build Castles In The Air
不切实际
Castles are usually enormous structures requiring strong foundations and the use of heavy construction materials such as stone.
城堡通常是一座巨型建筑，需要有坚实的地基，还会使用到沉重的建筑材料，例如石头等JFo8!%zqKtoFYCQkpq,。
If the foundations are not strong enough, the castle could collapse.
如果城堡的地基不够牢固，很可能会坍塌dpY(d3m*r0V]O.,w%yX。

The idea of building a castle in the air－with no foundation at all－is, of course, ridiculous.
在空中建一座城堡是没有地基的!2[FDG~@&ZS.5w。因此，“空中楼阁”当然是一个很荒谬的主意hzb5!k~S)~RlK6,=*1^。
That is why this idiom is used to describe ideas that are not realistic, as if they are dreams or fantasies.
因此，我们可以使用这个成语形容那些不切实际的想法——只不过是梦想或幻想Ds0mf(-f_r4a!。

译文来自可可英语