unearthly; otherworldly; out of this world
Set phrase describing something so beautiful, strange, or extraordinary that it seems not of this world. Often used for music, art, or experiences. The negative form 思えぬ is a classical/literary equivalent of 思えない.
See also: この世のものとも思えない
Her singing voice had an unearthly beauty.
その景色はこの世のものとも思えぬほど幻想的だった。
The scenery was so fantastical it seemed out of this world.
Phrase composed of この世 (this world), の (possessive), もの (thing), とも (even as), 思えぬ (classical negative of 思う, think). Literally 'cannot even think of as a thing of this world'.