Meaning of 幻想 in Japanese

He seems to be possessed with idle fancies.

The midnight sun is a fantastic natural phenomenon.

Sometimes reality and fantasy are hard to distinguish.

Permanent peace is nothing but an illusion.

Reality and fantasy are hard to distinguish.

Permanent peace is nothing but an illusion.

How is it that otherwise reasonable people come to believe that this same roof, that practically vanishing commodity, is freely obtainable just by packing up and going to another country?

Your idea is, as it were, a castle in the air.